Problema risolto (per fortuna)!
A fare tutto 'sto casino era "Xvid": una volta cancellato, tutto è tornato a posto. Solo che la segnalazione errori Microsoft ci ha messo un po' a dirmi che il problema era quello, fino a prima non risultava nulla...

Allora...Trend micro ha rilevato joke_noia.b (virus) e crck_wincmd.a (spyware). Dovrebbe averli cancellati, speriamo in bene...

So che il post è un po' vecchio, ma speravo in un aiuto dai moderatori (o da chiunque...): ho il solito problema "explorer.exe"!
Dunque, ho già scaricato l'aggiornamento windows, ma non ha sortito alcun effetto. Nei vecchi messaggi suggerite di formattare o fare il punto di ripristino, ma il fatto è che con eMule e Torrent perderei un casino di dati...insomma vorrei prima tentare di risolvere la cosa in altro modo, se possibile (e tenermi la formattazione come ultima spiaggia).

Questo è il rapporto di HiJack:

Logfile of Trend Micro HijackThis v2.0.2
Scan saved at 21.27.27, on 17/03/2008
Platform: Windows XP SP2 (WinNT 5.01.2600)
MSIE: Internet Explorer v7.00 (7.00.6000.16608)
Boot mode: Normal

Running processes:
C:\WINDOWS\System32\smss.exe
C:\WINDOWS\system32\winlogon.exe
C:\WINDOWS\system32\services.exe
C:\WINDOWS\system32\lsass.exe
C:\WINDOWS\system32\svchost.exe
C:\WINDOWS\System32\svchost.exe
C:\WINDOWS\system32\svchost.exe
C:\Programmi\Alwil Software\Avast4\aswUpdSv.exe
C:\Programmi\Alwil Software\Avast4\ashServ.exe
C:\WINDOWS\Explorer.EXE
C:\WINDOWS\system32\spoolsv.exe
C:\Programmi\Nero\Nero8\Nero BackItUp\NBService.exe
C:\WINDOWS\system32\svchost.exe
C:\Programmi\Alwil Software\Avast4\ashMaiSv.exe
C:\Programmi\Alwil Software\Avast4\ashWebSv.exe
C:\WINDOWS\system32\nvraidservice.exe
C:\WINDOWS\SOUNDMAN.EXE
C:\Programmi\HP\HP Software Update\HPWuSchd2.exe
C:\PROGRA~1\ALWILS~1\Avast4\ashDisp.exe
C:\Programmi\CyberLink\PowerDVD\PDVDServ.exe
C:\WINDOWS\system32\ctfmon.exe
C:\Programmi\Uniblue\SpeedUpMyPC 3\SpeedUpMyPC.exe
C:\Programmi\Creative\Sync Manager Unicode\CTSyncU.exe
C:\Programmi\HP\Digital Imaging\bin\hpqtra08.exe
C:\WINDOWS\system32\wbem\unsecapp.exe
C:\Programmi\HP\Digital Imaging\bin\hpqSTE08.exe
C:\Programmi\HP\Digital Imaging\Product Assistant\bin\hprblog.exe
C:\Programmi\File comuni\Nero\Lib\NMIndexStoreSvr.exe
C:\Programmi\File comuni\Nero\Lib\NMIndexingService.exe
C:\WINDOWS\System32\svchost.exe
C:\Programmi\Mozilla Firefox\firefox.exe
C:\Programmi\Trend Micro\HijackThis\HijackThis.exe

R0 - HKCU\Software\Microsoft\Internet Explorer\Main,Start Page = http://www.daemon-search.com/startpage
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 - HKCU\Software\Microsoft\Internet Explorer\Toolbar,LinksFolderName = Collegamenti
O2 - BHO: Supporto di collegamento per Adobe PDF Reader - {06849E9F-C8D7-4D59-B87D-784B7D6BE0B3} - C:\Programmi\File comuni\Adobe\Acrobat\ActiveX\AcroIEHelper.dll
O4 - HKLM\..\Run: [NVRaidService] C:\WINDOWS\system32\nvraidservice.exe
O4 - HKLM\..\Run: [SoundMan] SOUNDMAN.EXE
O4 - HKLM\..\Run: [HP Software Update] C:\Programmi\HP\HP Software Update\HPWuSchd2.exe
O4 - HKLM\..\Run: [Adobe Reader Speed Launcher] "C:\Programmi\Adobe\Reader 8.0\Reader\Reader_sl.exe"
O4 - HKLM\..\Run: [avast!] C:\PROGRA~1\ALWILS~1\Avast4\ashDisp.exe
O4 - HKLM\..\Run: [RemoteControl] C:\Programmi\CyberLink\PowerDVD\PDVDServ.exe
O4 - HKLM\..\Run: [Nero DriveSpeed] C:\PROGRA~1\Nero\NERO7~1\NEROTO~1\DRIVES~1.EXE
O4 - HKLM\..\Run: [NeroFilterCheck] C:\Programmi\File comuni\Nero\Lib\NeroCheck.exe
O4 - HKLM\..\Run: [NBKeyScan] "C:\Programmi\Nero\Nero8\Nero BackItUp\NBKeyScan.exe"
O4 - HKCU\..\Run: [CTFMON.EXE] C:\WINDOWS\system32\ctfmon.exe
O4 - HKCU\..\Run: [Uniblue SpeedUpMyPC] C:\Programmi\Uniblue\SpeedUpMyPC 3\SpeedUpMyPC.exe -s
O4 - HKCU\..\Run: [CTSyncU.exe] "C:\Programmi\Creative\Sync Manager Unicode\CTSyncU.exe"
O4 - HKUS\S-1-5-19\..\Run: [CTFMON.EXE] C:\WINDOWS\system32\CTFMON.EXE (User 'SERVIZIO LOCALE')
O4 - HKUS\S-1-5-20\..\Run: [CTFMON.EXE] C:\WINDOWS\system32\CTFMON.EXE (User 'SERVIZIO DI RETE')
O4 - HKUS\S-1-5-18\..\Run: [CTFMON.EXE] C:\WINDOWS\system32\CTFMON.EXE (User 'SYSTEM')
O4 - HKUS\.DEFAULT\..\Run: [CTFMON.EXE] C:\WINDOWS\system32\CTFMON.EXE (User 'Default user')
O4 - Global Startup: HP Digital Imaging Monitor.lnk = C:\Programmi\HP\Digital Imaging\bin\hpqtra08.exe
O4 - Global Startup: Microsoft Office.lnk = C:\Programmi\Microsoft Office\Office10\OSA.EXE
O8 - Extra context menu item: E&sporta in Microsoft Excel - res://c:\PROGRA~1\MICROS~2\OFFICE11\EXCEL.EXE/3000
O9 - Extra button: Ricerche - {92780B25-18CC-41C8-B9BE-3C9C571A8263} - C:\PROGRA~1\MICROS~2\OFFICE11\REFIEBAR.DLL
O9 - Extra button: (no name) - {e2e2dd38-d088-4134-82b7-f2ba38496583} - C:\WINDOWS\Network Diagnostic\xpnetdiag.exe
O9 - Extra 'Tools' menuitem: @xpsp3res.dll,-20001 - {e2e2dd38-d088-4134-82b7-f2ba38496583} - C:\WINDOWS\Network Diagnostic\xpnetdiag.exe
O9 - Extra button: Messenger - {FB5F1910-F110-11d2-BB9E-00C04F795683} - C:\Programmi\Messenger\msmsgs.exe
O9 - Extra 'Tools' menuitem: Windows Messenger - {FB5F1910-F110-11d2-BB9E-00C04F795683} - C:\Programmi\Messenger\msmsgs.exe
O17 - HKLM\System\CCS\Services\Tcpip\..\{B69DEE47-DCD1-42FC-B062-6B2B04C9530B}: NameServer = 151.99.125.1,151.99.0.100
O18 - Protocol: skype4com - {FFC8B962-9B40-4DFF-9458-1830C7DD7F5D} - C:\PROGRA~1\FILECO~1\Skype\SKYPE4~1.DLL
O23 - Service: avast! iAVS4 Control Service (aswUpdSv) - ALWIL Software - C:\Programmi\Alwil Software\Avast4\aswUpdSv.exe
O23 - Service: avast! Antivirus - ALWIL Software - C:\Programmi\Alwil Software\Avast4\ashServ.exe
O23 - Service: avast! Mail Scanner - ALWIL Software - C:\Programmi\Alwil Software\Avast4\ashMaiSv.exe
O23 - Service: avast! Web Scanner - ALWIL Software - C:\Programmi\Alwil Software\Avast4\ashWebSv.exe
O23 - Service: Nero BackItUp Scheduler 3 - Nero AG - C:\Programmi\Nero\Nero8\Nero BackItUp\NBService.exe
O23 - Service: NMIndexingService - Nero AG - C:\Programmi\File comuni\Nero\Lib\NMIndexingService.exe
O23 - Service: Pml Driver HPZ12 - HP - C:\WINDOWS\system32\HPZipm12.exe

--
End of file - 5598 bytes

...e questo il rapporto di Avast virus Cleaner:

17/03/2008, 21.28.02
Memory scanning started...
No virus body found in memory.
Memory scanning finished (5,6s).
----------
Files scanning started...
C:\Documents and Settings\Utente\Impostazioni locali\Temp\Perflib_Perfdata_154.dat... file could not be scanned!
C:\WINDOWS\system32\drivers\sptd.sys... file could not be scanned!
C:\WINDOWS\Temp\Perflib_Perfdata_4d4.dat... file could not be scanned!
No virus body found.
Files scanning finished  (34107 files, 0 infected, 534,0s).
Drives scanned: C: D: E:
----------


Poi sto cercando di fare un controllo con Trend Micro Housecall.

Qualche suggerimento???