hola ElPiedra, de muchas gracias por responder y ayudar con mi problema:

segui los pasos que me dejaste:

*desactivé el antivirus (McAfee) y antispyware (AVG)
*cerré todas las ventanas, y programas que estaban en ejecución
*me bajé el combofix.exe, y teniendolo en mi escritorio, le di doble click.

una barrita, con la leyenda de ComboFix, se llenó, y al segundo, se abrió una ventana Dos, azul, sucediendo esto:

y una ventana, ahora de windows, diciendome que "Freeware implementation of REG.EXE dejó de funcionar"
y lo cierra.
no hay reporte de combofix, ni menos...
no se que estaré haciendo mal, o qué está mal aca... pero por ejemplo, con el S&D, actualizado y todo, analiza buscando el virtumonde, y no lo encuentra.
la cosa no es asi, porque apenas abro el IE, saltan por lo menos 2 ventanitas de ad, o de direcciones varias.

hago una pregunta al paso: tenés alguna idea de que es "ms juan"? porque cada tanto, cuando ejecuto algun programa, aparece un aviso del S&D, justamente, notificandome un cambio en el registro... y me parecio bastante raro que un cambio de windows tuviera un nombre en especial...

dejo el registro de HJT, por si sirve, o cambió algo :S

Logfile of Trend Micro HijackThis v2.0.2
Scan saved at 11:56:06 p.m., on 20/01/2008
Platform: Windows Vista (WinNT 6.00.1904)
MSIE: Internet Explorer v7.00 (7.00.6000.16575)
Boot mode: Normal

Running processes:
C:\Windows\system32\Dwm.exe
C:\Program Files\McAfee\MPS\mpsevh.exe
C:\Windows\Explorer.EXE
C:\Program Files\Windows Defender\MSASCui.exe
C:\Program Files\ATI Technologies\ATI.ACE\Core-Static\MOM.EXE
C:\Program Files\HP\HP Software Update\hpwuSchd2.exe
C:\Program Files\Java\jre1.6.0_03\bin\jusched.exe
C:\Program Files\iTunes\iTunesHelper.exe
C:\Program Files\Windows Sidebar\sidebar.exe
C:\Windows\ehome\ehtray.exe
C:\Program Files\Spybot - Search & Destroy\TeaTimer.exe
C:\Program Files\Windows Media Player\wmpnscfg.exe
C:\Program Files\HP\Digital Imaging\bin\hpqtra08.exe
C:\Windows\ehome\ehmsas.exe
c:\PROGRA~1\mcafee.com\agent\mcagent.exe
C:\Program Files\Zabaware\HalReader\HalReader.exe
C:\Windows\system32\taskeng.exe
C:\Windows\system32\wbem\unsecapp.exe
C:\Program Files\HP\Digital Imaging\bin\hpqSTE08.exe
C:\Program Files\ATI Technologies\ATI.ACE\Core-Static\CCC.exe
C:\Windows\system32\conime.exe
C:\Program Files\MSN Messenger\msnmsgr.exe
C:\Program Files\Windows Media Player\wmplayer.exe
C:\Program Files\Mozilla Firefox\firefox.exe
C:\Program Files\Trend Micro\HijackThis\HijackThis.exe

R1 - HKCU\Software\Microsoft\Internet Explorer\Main,Search Page = http://go.microsoft.com/fwlink/?LinkId=54896
R1 - HKLM\Software\Microsoft\Internet Explorer\Main,Default_Page_URL = http://go.microsoft.com/fwlink/?LinkId=69157
R1 - HKLM\Software\Microsoft\Internet Explorer\Main,Default_Search_URL = http://go.microsoft.com/fwlink/?LinkId=54896
R1 - HKLM\Software\Microsoft\Internet Explorer\Main,Search Page = http://go.microsoft.com/fwlink/?LinkId=54896
R0 - HKLM\Software\Microsoft\Internet Explorer\Main,Start Page = http://go.microsoft.com/fwlink/?LinkId=69157
R0 - HKLM\Software\Microsoft\Internet Explorer\Search,SearchAssistant =
R0 - HKLM\Software\Microsoft\Internet Explorer\Search,CustomizeSearch =
R0 - HKCU\Software\Microsoft\Internet Explorer\Toolbar,LinksFolderName =
O1 - Hosts: ::1 localhost
O2 - BHO: Aplicación auxiliar de vínculos de Adobe PDF Reader - {06849E9F-C8D7-4D59-B87D-784B7D6BE0B3} - C:\Program Files\Common Files\Adobe\Acrobat\ActiveX\AcroIEHelper.dll
O2 - BHO: Megaupload Toolbar - {4E7BD74F-2B8D-469E-CCB0-B130EEDBE97C} - C:\PROGRA~1\MEGAUP~1\MEGAUP~1.DLL
O2 - BHO: Spybot-S&D IE Protection - {53707962-6F74-2D53-2644-206D7942484F} - C:\PROGRA~1\SPYBOT~1\SDHelper.dll
O2 - BHO: SSVHelper Class - {761497BB-D6F0-462C-B6EB-D4DAF1D92D43} - C:\Program Files\Java\jre1.6.0_03\bin\ssv.dll
O2 - BHO: scriptproxy - {7DB2D5A0-7241-4E79-B68D-6309F01C5231} - c:\PROGRA~1\mcafee\VIRUSS~1\scriptcl.dll
O2 - BHO: (no name) - {7E853D72-626A-48EC-A868-BA8D5E23E045} - (no file)
O2 - BHO: Google Toolbar Helper - {AA58ED58-01DD-4d91-8333-CF10577473F7} - c:\program files\google\googletoolbar1.dll
O2 - BHO: Google Toolbar Notifier BHO - {AF69DE43-7D58-4638-B6FA-CE66B5AD205D} - C:\Program Files\Google\GoogleToolbarNotifier\2.1.615.5858\sw g.dll
O3 - Toolbar: &Google - {2318C2B1-4965-11d4-9B18-009027A5CD4F} - c:\program files\google\googletoolbar1.dll
O3 - Toolbar: Megaupload Toolbar - {4E7BD74F-2B8D-469E-CCB0-B130EEDBE97C} - C:\PROGRA~1\MEGAUP~1\MEGAUP~1.DLL
O4 - HKLM\..\Run: [Windows Defender] %ProgramFiles%\Windows Defender\MSASCui.exe -hide
O4 - HKLM\..\Run: [S3Trayp] S3trayp.exe -chkautorun
O4 - HKLM\..\Run: [NeroFilterCheck] C:\Program Files\Common Files\Ahead\Lib\NeroCheck.exe
O4 - HKLM\..\Run: [StartCCC] C:\Program Files\ATI Technologies\ATI.ACE\Core-Static\CLIStart.exe
O4 - HKLM\..\Run: [HP Software Update] C:\Program Files\HP\HP Software Update\HPWuSchd2.exe
O4 - HKLM\..\Run: [SunJavaUpdateSched] "C:\Program Files\Java\jre1.6.0_03\bin\jusched.exe"
O4 - HKLM\..\Run: [Adobe Reader Speed Launcher] "C:\Program Files\Adobe\Reader 8.0\Reader\Reader_sl.exe"
O4 - HKLM\..\Run: [QuickTime Task] "C:\Program Files\QuickTime\QTTask.exe" -atboottime
O4 - HKLM\..\Run: [iTunesHelper] "C:\Program Files\iTunes\iTunesHelper.exe"
O4 - HKCU\..\Run: [Sidebar] C:\Program Files\Windows Sidebar\sidebar.exe /autoRun
O4 - HKCU\..\Run: [ehTray.exe] C:\Windows\ehome\ehTray.exe
O4 - HKCU\..\Run: [swg] C:\Program Files\Google\GoogleToolbarNotifier\GoogleToolbarNo tifier.exe
O4 - HKCU\..\Run: [SpybotSD TeaTimer] C:\Program Files\Spybot - Search & Destroy\TeaTimer.exe
O4 - HKCU\..\Run: [WMPNSCFG] C:\Program Files\Windows Media Player\WMPNSCFG.exe
O4 - HKUS\S-1-5-19\..\Run: [Sidebar] %ProgramFiles%\Windows Sidebar\Sidebar.exe /detectMem (User 'SERVICIO LOCAL')
O4 - HKUS\S-1-5-19\..\Run: [WindowsWelcomeCenter] rundll32.exe oobefldr.dll,ShowWelcomeCenter (User 'SERVICIO LOCAL')
O4 - HKUS\S-1-5-20\..\Run: [Sidebar] %ProgramFiles%\Windows Sidebar\Sidebar.exe /detectMem (User 'Servicio de red')
O4 - Global Startup: HP Digital Imaging Monitor.lnk = C:\Program Files\HP\Digital Imaging\bin\hpqtra08.exe
O4 - Global Startup: Ultra Hal Text-to-Speech Reader Startup.lnk = ?
O8 - Extra context menu item: E&xportar a Microsoft Excel - res://C:\PROGRA~1\MICROS~2\Office12\EXCEL.EXE/3000
O9 - Extra button: (no name) - {08B0E5C0-4FCB-11CF-AAA5-00401C608501} - C:\Program Files\Java\jre1.6.0_03\bin\ssv.dll
O9 - Extra 'Tools' menuitem: Consola de Sun Java - {08B0E5C0-4FCB-11CF-AAA5-00401C608501} - C:\Program Files\Java\jre1.6.0_03\bin\ssv.dll
O9 - Extra button: Research - {92780B25-18CC-41C8-B9BE-3C9C571A8263} - C:\PROGRA~1\MICROS~2\Office12\REFIEBAR.DLL
O9 - Extra button: PartyPoker.com - {B7FE5D70-9AA2-40F1-9C6B-12A255F085E1} - C:\Programs\PartyGaming\PartyPoker\RunApp.exe (file missing)
O9 - Extra 'Tools' menuitem: PartyPoker.com - {B7FE5D70-9AA2-40F1-9C6B-12A255F085E1} - C:\Programs\PartyGaming\PartyPoker\RunApp.exe (file missing)
O9 - Extra button: (no name) - {DFB852A3-47F8-48C4-A200-58CAB36FD2A2} - C:\PROGRA~1\SPYBOT~1\SDHelper.dll
O9 - Extra 'Tools' menuitem: Spybot - Search & Destroy Configuration - {DFB852A3-47F8-48C4-A200-58CAB36FD2A2} - C:\PROGRA~1\SPYBOT~1\SDHelper.dll
O10 - Unknown file in Winsock LSP: c:\windows\system32\wpclsp.dll
O10 - Unknown file in Winsock LSP: c:\windows\system32\wpclsp.dll
O10 - Unknown file in Winsock LSP: c:\windows\system32\wpclsp.dll
O10 - Unknown file in Winsock LSP: c:\windows\system32\wpclsp.dll
O10 - Unknown file in Winsock LSP: c:\windows\system32\wpclsp.dll
O10 - Unknown file in Winsock LSP: c:\windows\system32\wpclsp.dll
O10 - Unknown file in Winsock LSP: c:\windows\system32\wpclsp.dll
O10 - Unknown file in Winsock LSP: c:\windows\system32\wpclsp.dll
O10 - Unknown file in Winsock LSP: c:\windows\system32\wpclsp.dll
O13 - Gopher Prefix:
O16 - DPF: {C3F79A2B-B9B4-4A66-B012-3EE46475B072} (MessengerStatsClient Class) - http://messenger.zone.msn.com/binary/MessengerStatsPAClient.cab56907.cab
O16 - DPF: {D27CDB6E-AE6D-11CF-96B8-444553540000} (Shockwave Flash Object) - http://fpdownload2.macromedia.com/get/shockwave/cabs/flash/swflash.cab
O17 - HKLM\System\CCS\Services\Tcpip\..\{5837E163-8920-4973-B384-25913D47473F}: NameServer = 200.51.211.7 200.51.212.7
O17 - HKLM\System\CS1\Services\Tcpip\..\{5837E163-8920-4973-B384-25913D47473F}: NameServer = 200.51.211.7 200.51.212.7
O23 - Service: Apple Mobile Device - Apple, Inc. - C:\Program Files\Common Files\Apple\Mobile Device Support\bin\AppleMobileDeviceService.exe
O23 - Service: Ares Chatroom server (AresChatServer) - Ares Development Group - C:\Program Files\Ares\chatServer.exe
O23 - Service: Ati External Event Utility - ATI Technologies Inc. - C:\Windows\system32\Ati2evxx.exe
O23 - Service: ##Id_String1.6844F930_1628_4223_B5CC_5BB94B879762# # (Bonjour Service) - Apple Computer, Inc. - C:\Program Files\Bonjour\mDNSResponder.exe
O23 - Service: McAfee E-mail Proxy (Emproxy) - McAfee, Inc. - C:\PROGRA~1\COMMON~1\McAfee\EmProxy\emproxy.exe
O23 - Service: FLEXnet Licensing Service - Macrovision Europe Ltd. - C:\Program Files\Common Files\Macrovision Shared\FLEXnet Publisher\FNPLicensingService.exe
O23 - Service: Google Updater Service (gusvc) - Google - C:\Program Files\Google\Common\Google Updater\GoogleUpdaterService.exe
O23 - Service: Servicio del iPod (iPod Service) - Apple Inc. - C:\Program Files\iPod\bin\iPodService.exe
O23 - Service: McAfee HackerWatch Service - McAfee, Inc. - C:\Program Files\Common Files\McAfee\HackerWatch\HWAPI.exe
O23 - Service: McAfee Update Manager (mcmispupdmgr) - McAfee, Inc. - C:\PROGRA~1\McAfee\MSC\mcupdmgr.exe
O23 - Service: McAfee Services (mcmscsvc) - McAfee, Inc. - C:\PROGRA~1\McAfee\MSC\mcmscsvc.exe
O23 - Service: McAfee Network Agent (McNASvc) - McAfee, Inc. - c:\PROGRA~1\COMMON~1\mcafee\mna\mcnasvc.exe
O23 - Service: McAfee Scanner (McODS) - McAfee, Inc. - C:\PROGRA~1\McAfee\VIRUSS~1\mcods.exe
O23 - Service: McAfee Protection Manager (mcpromgr) - McAfee, Inc. - C:\PROGRA~1\McAfee\MSC\mcpromgr.exe
O23 - Service: McAfee Proxy Service (McProxy) - McAfee, Inc. - c:\PROGRA~1\COMMON~1\mcafee\mcproxy\mcproxy.exe
O23 - Service: McAfee Redirector Service (McRedirector) - McAfee, Inc. - c:\PROGRA~1\COMMON~1\mcafee\redirsvc\redirsvc.exe
O23 - Service: McAfee Real-time Scanner (McShield) - McAfee, Inc. - C:\PROGRA~1\McAfee\VIRUSS~1\mcshield.exe
O23 - Service: McAfee SystemGuards (McSysmon) - McAfee, Inc. - C:\PROGRA~1\McAfee\VIRUSS~1\mcsysmon.exe
O23 - Service: McAfee Personal Firewall Service (MpfService) - McAfee, Inc. - C:\Program Files\McAfee\MPF\MPFSrv.exe
O23 - Service: McAfee Privacy Service (MPS9) - McAfee, Inc. - C:\PROGRA~1\McAfee\MPS\mps.exe
O23 - Service: UPnPService - Magix AG - C:\Program Files\Common Files\MAGIX Shared\UPnPService\UPnPService.exe

--
End of file - 9740 bytes

en serio muchas gracias por la mano que me estas dando con este tema, porque me esta poniendo un poco mal, tener que reiniciar la maquina, cada vez que desaparece el escritorio y la barra de herramientas asi como asi, y no puedo hacer nada, salvo mirar el sidebar...

saludos
kiwi*