Ok, solo che dovresti spiegarmi come si disattiva il ripristino di configurazione e come si fa partire la modalità provvisoria di Win XP.

Seconda cosa, ho fatto diverse prove disattivando una per volta alcune applicazioni da esegui - msconfig - avvio . Bene il problema non si presenta più disattivando queste due voci:
1- istinstall_zazzer
2- bundleouter 3401040401
Le ho disinsatllate ma non oso cancellarle perchè non so cosa sono. E' possibile che sono entrate con Kazaa Plus che poi cmq ho eliminato?
Questo è il log di HJ mi dai una occhiata? (l'ho inviato anche in altra rubrica):

Logfile of HijackThis v1.97.7
Scan saved at 17.21.31, on 04/09/2004
Platform: Windows XP SP1 (WinNT 5.01.2600)
MSIE: Internet Explorer v6.00 SP1 (6.00.2800.1106)

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\Ati2evxx.exe
C:\WINDOWS\system32\svchost.exe
C:\WINDOWS\System32\svchost.exe
C:\WINDOWS\system32\Ati2evxx.exe
C:\WINDOWS\Explorer.EXE
C:\WINDOWS\system32\spoolsv.exe
C:\PROGRA~1\Grisoft\AVG6\avgserv.exe
C:\Programmi\File comuni\Microsoft Shared\VS7DEBUG\MDM.EXE
C:\PROGRA~1\Agnitum\OUTPOS~1.0\outpost.exe
C:\Programmi\ATI Technologies\ATI Control Panel\atiptaxx.exe
C:\WINDOWS\System32\rundll32.exe
C:\PROGRA~1\Grisoft\AVG6\avgcc32.exe
C:\Programmi\Messenger\msmsgs.exe
C:\WINDOWS\System32\ctfmon.exe
C:\WINDOWS\System32\wuauclt.exe
C:\WINDOWS\System32\wuauclt.exe
C:\Documents and Settings\user\Desktop\Download\HijackThis.exe

R0 - HKCU\Software\Microsoft\Internet Explorer\Main,Start Page = http://www.virgilio.it/home/index.html
R0 - HKCU\Software\Microsoft\Internet Explorer\Toolbar,LinksFolderName = Collegamenti
O2 - BHO: (no name) - {06849E9F-C8D7-4D59-B87D-784B7D6BE0B3} - C:\Programmi\Adobe\Acrobat 5.0\Reader\ActiveX\AcroIEHelper.ocx
O2 - BHO: (no name) - {53707962-6F74-2D53-2644-206D7942484F} - C:\Programmi\Spybot - Search & Destroy\SDHelper.dll
O3 - Toolbar: &Radio - {8E718888-423F-11D2-876E-00A0C9082467} - C:\WINDOWS\System32\msdxm.ocx
O4 - HKLM\..\Run: [ATIPTA] C:\Programmi\ATI Technologies\ATI Control Panel\atiptaxx.exe
O4 - HKLM\..\Run: [NeroCheck] C:\WINDOWS\system32\NeroCheck.exe
O4 - HKLM\..\Run: [AdslTaskBar] rundll32.exe stmctrl.dll,TaskBar
O4 - HKLM\..\Run: [AVG_CC] C:\PROGRA~1\Grisoft\AVG6\avgcc32.exe /STARTUP
O4 - HKLM\..\Run: [Outpost Firewall] "C:\Programmi\Agnitum\Outpost Firewall 1.0\outpost.exe" /waitservice
O4 - HKLM\..\Run: [90ae34.exe] 90ae34.exe
O4 - HKLM\..\Run: [istinstall_zazzer.exe] istinstall_zazzer.exe
O4 - HKLM\..\Run: [bundleouter3401040401.exe] bundleouter3401040401.exe
O4 - HKCU\..\Run: [MSMSGS] "C:\Programmi\Messenger\msmsgs.exe" /background
O4 - HKCU\..\Run: [CTFMON.EXE] C:\WINDOWS\System32\ctfmon.exe
O8 - Extra context menu item: &Add animation to IncrediMail Style Box - C:\PROGRA~1\INCRED~1\bin\resources\WebMenuImg.htm
O8 - Extra context menu item: E&sporta in Microsoft Excel - res://C:\PROGRA~1\MICROS~2\OFFICE11\EXCEL.EXE/3000
O9 - Extra button: Ricerche (HKLM)
O9 - Extra button: Trashcan (HKCU)
O9 - Extra 'Tools' menuitem: Show Trashcan (HKCU)
O16 - DPF: {6414512B-B978-451D-A0D8-FCFDF33E833C} (WUWebControl Class) - http://v5.windowsupdate.microsoft.com/v5consumer/V5Controls/en/x86/client/wuweb_site.cab?1094307203734
O16 - DPF: {D27CDB6E-AE6D-11CF-96B8-444553540000} (Shockwave Flash Object) - http://download.macromedia.com/pub/shockwave/cabs/flash/swflash.cab
O16 - DPF: {F00F4763-7355-4725-82F7-0DA94A256D46} (IMDownloader Class) - http://www2.incredimail.com/contents/setup/downloader/imloader.cab
O17 - HKLM\System\CCS\Services\Tcpip\..\{8E2DD93D-08D9-4AD9-BF6C-E80CD75E8157}: NameServer = 62.211.69.150 212.48.4.15