questo è il log di hjt (sembra identico all'altro)
Logfile of Trend Micro HijackThis v2.0.2
Scan saved at 14.12.20, on 02/05/2010
Platform: Windows XP SP2 (WinNT 5.01.2600)
MSIE: Internet Explorer v8.00 (8.00.6001.18702)
Boot mode: Normal

Running processes:
C:\WINDOWS\System32\smss.exe
C:\WINDOWS\system32\csrss.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:\Programmi\COMODO\COMODO Internet Security\cmdagent.exe
C:\WINDOWS\system32\svchost.exe
C:\WINDOWS\system32\svchost.exe
C:\WINDOWS\system32\svchost.exe
C:\WINDOWS\system32\ZCfgSvc.exe
C:\WINDOWS\Explorer.EXE
C:\WINDOWS\system32\spoolsv.exe
C:\WINDOWS\system32\svchost.exe
C:\WINDOWS\ATKKBService.exe
C:\WINDOWS\system32\SupportAppMH\cdrom_mon.exe
C:\PROGRA~1\AVG\AVG8\avgwdsvc.exe
C:\Programmi\IObit\IObit Security 360\IS360srv.exe
C:\PROGRA~1\AVG\AVG8\avgrsx.exe
C:\Programmi\File comuni\Microsoft Shared\VS7DEBUG\MDM.EXE
C:\PROGRA~1\AVG\AVG8\avgnsx.exe
C:\Programmi\Nero\Nero8\Nero BackItUp\NBService.exe
C:\Programmi\IObit\IObit Security 360\IS360tray.exe
C:\Programmi\COMODO\COMODO Internet Security\cfp.exe
C:\WINDOWS\system32\ctfmon.exe
C:\Programmi\Telecom Italia\WanMiniport1st\srvany.exe
C:\Programmi\Telecom Italia\WanMiniport1st\WanMiniport1st_srv.exe
C:\WINDOWS\system32\svchost.exe
C:\Programmi\TeamViewer\Version4\TeamViewer_Service.exe
C:\Programmi\TomTom HOME 2\TomTomHOMEService.exe
C:\WINDOWS\System32\alg.exe
C:\Programmi\Malwarebytes' Anti-Malware\mbam.exe
C:\Programmi\IObit\IObit Security 360\is360.exe
C:\WINDOWS\system32\NOTEPAD.EXE
C:\Programmi\Internet Explorer\iexplore.exe
C:\Programmi\Internet Explorer\iexplore.exe
C:\Programmi\Trend Micro\HijackThis\HijackThis.exe
C:\WINDOWS\system32\wbem\wmiprvse.exe
C:\Programmi\Skype\Toolbars\Shared\SkypeNames.exe

R0 - HKCU\Software\Microsoft\Internet Explorer\Main,Start Page = http://www.google.it/
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
O2 - BHO: AcroIEHelperStub - {18DF081C-E8AD-4283-A596-FA578C2EBDC3} - C:\Programmi\File comuni\Adobe\Acrobat\ActiveX\AcroIEHelperShim.dll
O2 - BHO: Skype add-on (mastermind) - {22BF413B-C6D2-4d91-82A9-A0F997BA588C} - C:\Programmi\Skype\Toolbars\Internet Explorer\SkypeIEPlugin.dll
O2 - BHO: WormRadar.com IESiteBlocker.NavFilter - {3CA2F312-6F6E-4B53-A66E-4E65E497C8C0} - C:\Programmi\AVG\AVG8\avgssie.dll
O2 - BHO: (no name) - {5C255C8A-E604-49b4-9D64-90988571CECB} - (no file)
O2 - BHO: Groove GFS Browser Helper - {72853161-30C5-4D22-B7F9-0BBC1D38A37E} - C:\Programmi\Microsoft Office\Office12\GrooveShellExtensions.dll
O2 - BHO: Guida per l'accesso a Windows Live - {9030D464-4C02-4ABF-8ECC-5164760863C6} - C:\Programmi\File comuni\Microsoft Shared\Windows Live\WindowsLiveLogin.dll
O4 - HKLM\..\Run: [IObit Security 360] "C:\Programmi\IObit\IObit Security 360\IS360tray.exe" /autostart
O4 - HKLM\..\Run: [COMODO Internet Security] "C:\Programmi\COMODO\COMODO Internet Security\cfp.exe" -h
O4 - HKCU\..\Run: [ctfmon.exe] C:\WINDOWS\system32\ctfmon.exe
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')
O6 - HKCU\Software\Policies\Microsoft\Internet Explorer\Control Panel present
O8 - Extra context menu item: E&sporta in Microsoft Excel - res://C:\PROGRA~1\MICROS~2\OFFICE11\EXCEL.EXE/3000
O8 - Extra context menu item: E&xport to Microsoft Excel - res://C:\PROGRA~1\MICROS~2\Office12\EXCEL.EXE/3000
O8 - Extra context menu item: Google Sidewiki... - res://C:\Programmi\Google\Google Toolbar\Component\GoogleToolbarDynamic_mui_en_96D6FF0C6D236BF8.dll/cmsidewiki.html
O9 - Extra button: Send to OneNote - {2670000A-7350-4f3c-8081-5663EE0C6C49} - C:\PROGRA~1\MICROS~2\Office12\ONBttnIE.dll
O9 - Extra 'Tools' menuitem: S&end to OneNote - {2670000A-7350-4f3c-8081-5663EE0C6C49} - C:\PROGRA~1\MICROS~2\Office12\ONBttnIE.dll
O9 - Extra button: 4APoker - {47DDC1F4-8611-4f89-806E-3CBD8B7F924F} - C:\Programmi\4A\4APoker\RunApp.exe
O9 - Extra 'Tools' menuitem: 4APoker - {47DDC1F4-8611-4f89-806E-3CBD8B7F924F} - C:\Programmi\4A\4APoker\RunApp.exe
O9 - Extra button: (no name) - {5067A26B-1337-4436-8AFE-EE169C2DA79F} - C:\Programmi\Skype\Toolbars\Internet Explorer\SkypeIEPlugin.dll
O9 - Extra 'Tools' menuitem: Skype add-on for Internet Explorer - {5067A26B-1337-4436-8AFE-EE169C2DA79F} - C:\Programmi\Skype\Toolbars\Internet Explorer\SkypeIEPlugin.dll
O9 - Extra button: Skype - {77BF5300-1474-4EC7-9980-D32B190E9B07} - C:\Programmi\Skype\Toolbars\Internet Explorer\SkypeIEPlugin.dll
O9 - Extra button: Research - {92780B25-18CC-41C8-B9BE-3C9C571A8263} - C:\PROGRA~1\MICROS~2\Office12\REFIEBAR.DLL
O9 - Extra button: Messenger - {FB5F1910-F110-11d2-BB9E-00C04F795683} - C:\Programmi\Messenger\msmsgs.exe (file missing)
O9 - Extra 'Tools' menuitem: Windows Messenger - {FB5F1910-F110-11d2-BB9E-00C04F795683} - C:\Programmi\Messenger\msmsgs.exe (file missing)
O14 - IERESET.INF: START_PAGE_URL=http://www.asus.com
O16 - DPF: {E2883E8F-472F-4FB0-9522-AC9BF37916A7} - http://platformdl.adobe.com/NOS/getPlusPlus/1.6/gp.cab
O18 - Protocol: grooveLocalGWS - {88FED34C-F0CA-4636-A375-3CB6248B04CD} - C:\Programmi\Microsoft Office\Office12\GrooveSystemServices.dll
O18 - Protocol: linkscanner - {F274614C-63F8-47D5-A4D1-FBDDE494F8D1} - C:\Programmi\AVG\AVG8\avgpp.dll
O20 - Winlogon Notify: avgrsstarter - C:\WINDOWS\SYSTEM32\avgrsstx.dll
O23 - Service: ATK Keyboard Service (ATKKeyboardService) - ASUSTeK COMPUTER INC. - C:\WINDOWS\ATKKBService.exe
O23 - Service: Autorun CDROM Monitor - Unknown owner - C:\WINDOWS\system32\SupportAppMH\cdrom_mon.exe
O23 - Service: AVG Free8 WatchDog (avg8wd) - AVG Technologies CZ, s.r.o. - C:\PROGRA~1\AVG\AVG8\avgwdsvc.exe
O23 - Service: COMODO Internet Security Helper Service (cmdAgent) - COMODO - C:\Programmi\COMODO\COMODO Internet Security\cmdagent.exe
O23 - Service: Google Update Service (gupdate1c98d3f1537111a) (gupdate1c98d3f1537111a) - Google Inc. - C:\Programmi\Google\Update\GoogleUpdate.exe
O23 - Service: Google Software Updater (gusvc) - Google - C:\Programmi\Google\Common\Google Updater\GoogleUpdaterService.exe
O23 - Service: IS360service - IObit - C:\Programmi\IObit\IObit Security 360\IS360srv.exe
O23 - Service: Nero BackItUp Scheduler 3 - Nero AG - C:\Programmi\Nero\Nero8\Nero BackItUp\NBService.exe
O23 - Service: Network WanMiniport First Position - Unknown owner - C:\Programmi\Telecom Italia\WanMiniport1st\srvany.exe
O23 - Service: NMIndexingService - Nero AG - C:\Programmi\File comuni\Nero\Lib\NMIndexingService.exe
O23 - Service: StarWind AE Service (StarWindServiceAE) - Unknown owner - C:\Programmi\Alcohol Soft\Alcohol 120\StarWind\StarWindServiceAE.exe (file missing)
O23 - Service: TeamViewer 4 (TeamViewer4) - TeamViewer GmbH - C:\Programmi\TeamViewer\Version4\TeamViewer_Service.exe
O23 - Service: TomTomHOMEService - TomTom - C:\Programmi\TomTom HOME 2\TomTomHOMEService.exe

--
End of file - 7709 bytes


equesto è di malwarebytes

Malwarebytes' Anti-Malware 1.46
www.malwarebytes.org

Versione database: 4058

Windows 5.1.2600 Service Pack 2
Internet Explorer 8.0.6001.18702

02/05/2010 13.35.17
mbam-log-2010-05-02 (13-35-17).txt

Tipo di scansione: Scansione completa (C:\|)
Elementi esaminati: 160838
Tempo trascorso: 57 minuti, 17 secondi

Processi infetti in memoria: 0
Moduli di memoria infetti: 0
Chiavi di registro infette: 0
Valori di registro infetti: 0
Voci infette nei dati di registro: 0
Cartelle infette: 0
File infetti: 0

Processi infetti in memoria:
(Non sono stati rilevati elementi nocivi)

Moduli di memoria infetti:
(Non sono stati rilevati elementi nocivi)

Chiavi di registro infette:
(Non sono stati rilevati elementi nocivi)

Valori di registro infetti:
(Non sono stati rilevati elementi nocivi)

Voci infette nei dati di registro:
(Non sono stati rilevati elementi nocivi)

Cartelle infette:
(Non sono stati rilevati elementi nocivi)

File infetti:
(Non sono stati rilevati elementi nocivi)

no, non ho atri problemi, grazie cmq

AVG non lo uso ma non riesco nemmeno a toglierlo perchè mi da un problema con la chiave di registro, uso comodo come antivirus

Bene...AVG eliminato, grazie!!

Hai idea cosa può essere e come posso risolvere questo problema:
quando spengo il computer mi appare una finestra con scritto chiusura programma Sample(o qualcosa del genere) quando pigio termina adesso il pc si arresta

A parte il tuo problema, ti consiglio di installare il Service Pack 3 altrimenti non ti sarà più possibile scaricare gli aggiornamenti di XP, oltre a questo avrai maggior protezione.