grazie Steven 75 per il tuo interessamento. Ho provato a fare la scansione con Ewido ma non ho risolto il problema, inizio ad essere davvero disperato..... Ho anche installato un nuovo browser, mozilla firefox, ma non riesco a bloccare explorer, tant'è che il virus continua ad aprirmi la pagina iniziale di internet explorer. Riporto il log. della versione di hijackthis che tu mi hai gentilmente suggerito:

Logfile of HijackThis v1.99.1
Scan saved at 0.36.39, on 01/05/2006
Platform: Windows XP SP2 (WinNT 5.01.2600)
MSIE: Internet Explorer v6.00 SP2 (6.00.2900.2180)

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:\Programmi\Windows Defender\MsMpEng.exe
C:\WINDOWS\System32\svchost.exe
C:\WINDOWS\system32\spoolsv.exe
C:\WINDOWS\Explorer.EXE
C:\Programmi\Alwil Software\Avast4\aswUpdSv.exe
C:\WINDOWS\System32\Ati2evxx.exe
C:\Programmi\Alwil Software\Avast4\ashServ.exe
C:\Programmi\File comuni\EPSON\EBAPI\SAgent2.exe
C:\Programmi\ewido anti-malware\ewidoctrl.exe
C:\Programmi\ewido anti-malware\ewidoguard.exe
C:\WINDOWS\system32\atiptaxx.exe
C:\Programmi\Apoint2K\Apoint.exe
C:\PROGRA~1\EzButton\CPATR10.EXE
C:\WINDOWS\system32\slserv.exe
C:\Programmi\Winamp\Winampa.exe
C:\WINDOWS\System32\svchost.exe
C:\PROGRA~1\DAP\DAP.EXE
C:\WINDOWS\system32\fxssvc.exe
C:\Programmi\Apoint2K\Apntex.exe
C:\WINDOWS\System32\spool\DRIVERS\W32X86\3\E_S10IC 2.EXE
C:\Programmi\iTunes\iTunesHelper.exe
C:\Programmi\QuickTime\qttask.exe
C:\Programmi\Windows Defender\MSASCui.exe
C:\PROGRA~1\ALWILS~1\Avast4\ashDisp.exe
C:\WINDOWS\system32\ctfmon.exe
C:\Programmi\Messenger\msmsgs.exe
C:\Programmi\Microsoft Office\Office\OSA.EXE
C:\Programmi\Alwil Software\Avast4\ashMaiSv.exe
C:\Programmi\Alwil Software\Avast4\ashWebSv.exe
C:\Programmi\iPod\bin\iPodService.exe
C:\Programmi\Hijackthis\HijackThis.exe

R0 - HKCU\Software\Microsoft\Internet Explorer\Main,Start Page = http://www.fastweb.it/
R1 - HKLM\Software\Microsoft\Internet Explorer\Main,Default_Page_URL = http://www.fastweb.it
R1 - HKCU\Software\Microsoft\Internet Explorer\Main,Window Title = Microsoft Internet Explorer fornito da FastWeb
R1 - HKCU\Software\Microsoft\Windows\CurrentVersion\Int ernet Settings,ProxyOverride = ;<local>
R0 - HKCU\Software\Microsoft\Internet Explorer\Toolbar,LinksFolderName = Collegamenti
O2 - BHO: DAPHelper Class - {0000CC75-ACF3-4cac-A0A9-DD3868E06852} - C:\Programmi\DAP\DAPBHO.dll
O2 - BHO: AcroIEHlprObj Class - {06849E9F-C8D7-4D59-B87D-784B7D6BE0B3} - C:\Programmi\Adobe\Acrobat 5.0\Reader\ActiveX\AcroIEHelper.ocx
O3 - Toolbar: DAP Bar - {62999427-33FC-4baf-9C9C-BCE6BD127F08} - C:\Programmi\DAP\DAPIEBar.dll
O4 - HKLM\..\Run: [ATIModeChange] Ati2mdxx.exe
O4 - HKLM\..\Run: [AtiPTA] atiptaxx.exe
O4 - HKLM\..\Run: [Apoint] C:\Programmi\Apoint2K\Apoint.exe
O4 - HKLM\..\Run: [CPATR10] C:\PROGRA~1\EzButton\CPATR10.EXE
O4 - HKLM\..\Run: [WinampAgent] "C:\Programmi\Winamp\Winampa.exe"
O4 - HKLM\..\Run: [NeroCheck] C:\WINDOWS\system32\NeroCheck.exe
O4 - HKLM\..\Run: [DownloadAccelerator] C:\PROGRA~1\DAP\DAP.EXE /STARTUP
O4 - HKLM\..\Run: [CloneCDElbyCDFL] "C:\Programmi\Elaborate Bytes\CloneCD\ElbyCheck.exe" /L ElbyCDFL
O4 - HKLM\..\Run: [Ad-aware] "C:\Programmi\Lavasoft\Ad-aware 6\Ad-aware.exe" +c
O4 - HKLM\..\Run: [EPSON Stylus C44 Series] C:\WINDOWS\System32\spool\DRIVERS\W32X86\3\E_S10IC 2.EXE /P23 "EPSON Stylus C44 Series" /O6 "USB001" /M "Stylus C44"
O4 - HKLM\..\Run: [iTunesHelper] "C:\Programmi\iTunes\iTunesHelper.exe"
O4 - HKLM\..\Run: [QuickTime Task] "C:\Programmi\QuickTime\qttask.exe" -atboottime
O4 - HKLM\..\Run: [Windows Defender] "C:\Programmi\Windows Defender\MSASCui.exe" -hide
O4 - HKLM\..\Run: [avast!] C:\PROGRA~1\ALWILS~1\Avast4\ashDisp.exe
O4 - HKCU\..\Run: [CTFMON.EXE] C:\WINDOWS\system32\ctfmon.exe
O4 - HKCU\..\Run: [MSMSGS] "C:\Programmi\Messenger\msmsgs.exe" /background
O4 - Global Startup: Avvio Office.lnk = C:\Programmi\Microsoft Office\Office\OSA.EXE
O4 - Global Startup: Ricerca rapida.lnk = C:\Programmi\Microsoft Office\Office\FINDFAST.EXE
O8 - Extra context menu item: &Download with &DAP - C:\PROGRA~1\DAP\dapextie.htm
O8 - Extra context menu item: Download &all with DAP - C:\PROGRA~1\DAP\dapextie2.htm
O9 - Extra button: (no name) - {08B0E5C0-4FCB-11CF-AAA5-00401C608501} - C:\Programmi\Java\j2re1.4.1_01\bin\npjpi141_01.dll
O9 - Extra 'Tools' menuitem: Sun Java Console - {08B0E5C0-4FCB-11CF-AAA5-00401C608501} - C:\Programmi\Java\j2re1.4.1_01\bin\npjpi141_01.dll
O9 - Extra button: Run DAP - {669695BC-A811-4A9D-8CDF-BA8C795F261C} - C:\PROGRA~1\DAP\DAP.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
O9 - Extra button: Alice - {33CFC9E3-59FB-49A7-BA4F-DB5FADB8AD55} - http://gw.aliceadsl.it/alice (file missing) (HKCU)
O9 - Extra button: Umail - {A9C00CCB-913D-4725-82E4-C59FA3A1BE9B} - http://www.umail.it (file missing) (HKCU)
O14 - IERESET.INF: START_PAGE_URL=http://www.fastweb.it
O16 - DPF: {17492023-C23A-453E-A040-C7C580BBF700} (Windows Genuine Advantage Validation Tool) - http://go.microsoft.com/fwlink/?linkid=39204
O16 - DPF: {6E32070A-766D-4EE6-879C-DC1FA91D2FC3} (MUWebControl Class) - http://update.microsoft.com/microso...b?1146241929652
O18 - Protocol: msnim - {828030A1-22C1-4009-854F-8E305202313F} - "C:\PROGRA~1\MSNMES~1\msgrapp.dll" (file missing)
O23 - Service: avast! iAVS4 Control Service (aswUpdSv) - Unknown owner - C:\Programmi\Alwil Software\Avast4\aswUpdSv.exe
O23 - Service: Ati HotKey Poller - Unknown owner - C:\WINDOWS\System32\Ati2evxx.exe
O23 - Service: avast! Antivirus - Unknown owner - C:\Programmi\Alwil Software\Avast4\ashServ.exe
O23 - Service: avast! Mail Scanner - Unknown owner - C:\Programmi\Alwil Software\Avast4\ashMaiSv.exe" /service (file missing)
O23 - Service: avast! Web Scanner - Unknown owner - C:\Programmi\Alwil Software\Avast4\ashWebSv.exe" /service (file missing)
O23 - Service: EPSON Printer Status Agent2 (EPSONStatusAgent2) - SEIKO EPSON CORPORATION - C:\Programmi\File comuni\EPSON\EBAPI\SAgent2.exe
O23 - Service: ewido security suite control - ewido networks - C:\Programmi\ewido anti-malware\ewidoctrl.exe
O23 - Service: ewido security suite guard - ewido networks - C:\Programmi\ewido anti-malware\ewidoguard.exe
O23 - Service: InstallDriver Table Manager (IDriverT) - Macrovision Corporation - C:\Programmi\File comuni\InstallShield\Driver\11\Intel 32\IDriverT.exe
O23 - Service: iPodService - Apple Computer, Inc. - C:\Programmi\iPod\bin\iPodService.exe
O23 - Service: SmartLinkService (SLService) - - C:\WINDOWS\SYSTEM32\slserv.exe