Dopo i tanti problemi riscontrati nel vecchio computer, ho fatto il grande passo.
Ho ordinato un nuovo PC, Intel Dual Core 3.16 Ghz, 4 Gb di ram, Windows XP, scheda video ASUS. Collegato a Internet con router Alice e protetto da gruppo di continuità Riello.
Il tutto ritirato venerdì pomeriggio.
Ci ho lavorato venerdì fino a notte inoltrata, l'intero sabato e quasi l'intera domenica, senza riscontrare alcun problema di sorta.
Questa sera l'ho acceso alle 21, mentre entravo in google si è autoresettato. Passi. Poi più nessun problema, dopo il riavvio, ma dieci minuti fa si è autoresettato di nuovo... :-(((
Questo è hjt. Ditemi che è tutto pulito...

Logfile of Trend Micro HijackThis v2.0.2
Scan saved at 23.07.59, on 06/04/2009
Platform: Windows XP SP3 (WinNT 5.01.2600)
MSIE: Internet Explorer v7.00 (7.00.6000.16791)
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\Ati2evxx.exe
C:\WINDOWS\system32\svchost.exe
C:\WINDOWS\System32\svchost.exe
C:\WINDOWS\system32\Ati2evxx.exe
C:\WINDOWS\system32\spoolsv.exe
C:\WINDOWS\Explorer.EXE
C:\PROGRA~1\AVG\AVG8\avgwdsvc.exe
C:\Programmi\Canon\IJPLM\IJPLMSVC.EXE
C:\Programmi\Java\jre6\bin\jqs.exe
C:\Programmi\Telecom Italia\WanMiniport1st\srvany.exe
C:\WINDOWS\system32\svchost.exe
C:\Programmi\Telecom Italia\WanMiniport1st\WanMiniport1st_srv.exe
C:\PROGRA~1\AVG\AVG8\avgrsx.exe
C:\PROGRA~1\AVG\AVG8\avgemc.exe
C:\PROGRA~1\AVG\AVG8\avgnsx.exe
C:\WINDOWS\RTHDCPL.EXE
C:\Programmi\ATI Technologies\ATI.ACE\Core-Static\MOM.exe
C:\PROGRA~1\AVG\AVG8\avgtray.exe
C:\Programmi\AVG\AVG8\avgcsrvx.exe
C:\PROGRA~1\ALICET~1\SMARTB~1\MotiveSB.exe
C:\PROGRA~1\ALICET~1\vendors\AliceRE\content\template\DRIVEN~1\syncer\MCCITR~1.EXE
C:\Programmi\Java\jre6\bin\jusched.exe
C:\Programmi\Canon\MyPrinter\BJMyPrt.exe
C:\WINDOWS\system32\ctfmon.exe
C:\Programmi\File comuni\Ahead\Lib\NMBgMonitor.exe
C:\Programmi\File comuni\Ahead\Lib\NMIndexStoreSvr.exe
C:\Programmi\Alice ti aiuta\bin\mpbtn.exe
C:\Programmi\ATI Technologies\ATI.ACE\Core-Static\ccc.exe
C:\Programmi\File comuni\Ahead\Lib\NMIndexingService.exe
C:\WINDOWS\system32\wuauclt.exe
C:\Programmi\7-Zip\7zFM.exe
C:\DOCUME~1\pc\IMPOST~1\Temp\7zO1.tmp\HijackThis.exe

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
R1 - HKCU\Software\Microsoft\Windows\CurrentVersion\Internet Settings,ProxyOverride = 127.0.0.1
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: 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: Guida per l'accesso a Windows Live - {9030D464-4C02-4ABF-8ECC-5164760863C6} - C:\Programmi\File comuni\Microsoft Shared\Windows Live\WindowsLiveLogin.dll
O2 - BHO: Java(tm) Plug-In 2 SSV Helper - {DBC80044-A445-435b-BC74-9C25C1C588A9} - C:\Programmi\Java\jre6\bin\jp2ssv.dll
O2 - BHO: JQSIEStartDetectorImpl - {E7E6F031-17CE-4C07-BC86-EABFE594F69C} - C:\Programmi\Java\jre6\lib\deploy\jqs\ie\jqs_plugin.dll
O4 - HKLM\..\Run: [RTHDCPL] RTHDCPL.EXE
O4 - HKLM\..\Run: [Alcmtr] ALCMTR.EXE
O4 - HKLM\..\Run: [StartCCC] "C:\Programmi\ATI Technologies\ATI.ACE\Core-Static\CLIStart.exe" MSRun
O4 - HKLM\..\Run: [AVG8_TRAY] C:\PROGRA~1\AVG\AVG8\avgtray.exe
O4 - HKLM\..\Run: [Motive SmartBridge] C:\PROGRA~1\ALICET~1\SMARTB~1\MotiveSB.exe
O4 - HKLM\..\Run: [AliceRE_McciTrayApp] C:\PROGRA~1\ALICET~1\vendors\AliceRE\content\template\DRIVEN~1\syncer\MCCITR~1.EXE
O4 - HKLM\..\Run: [SunJavaUpdateSched] "C:\Programmi\Java\jre6\bin\jusched.exe"
O4 - HKLM\..\Run: [CanonMyPrinter] C:\Programmi\Canon\MyPrinter\BJMyPrt.exe /logon
O4 - HKCU\..\Run: [ctfmon.exe] C:\WINDOWS\system32\ctfmon.exe
O4 - HKCU\..\Run: [BgMonitor_{79662E04-7C6C-4d9f-84C7-88D8A56B10AA}] "C:\Programmi\File comuni\Ahead\Lib\NMBgMonitor.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: Alice ti aiuta.lnk = C:\Programmi\Alice ti aiuta\bin\matcli.exe
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
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: Ati HotKey Poller - ATI Technologies Inc. - C:\WINDOWS\system32\Ati2evxx.exe
O23 - Service: ATI Smart - Unknown owner - C:\WINDOWS\system32\ati2sgag.exe
O23 - Service: AVG Free8 E-mail Scanner (avg8emc) - AVG Technologies CZ, s.r.o. - C:\PROGRA~1\AVG\AVG8\avgemc.exe
O23 - Service: AVG Free8 WatchDog (avg8wd) - AVG Technologies CZ, s.r.o. - C:\PROGRA~1\AVG\AVG8\avgwdsvc.exe
O23 - Service: Inkjet Printer/Scanner Extended Survey Program (IJPLMSVC) - Unknown owner - C:\Programmi\Canon\IJPLM\IJPLMSVC.EXE
O23 - Service: Java Quick Starter (JavaQuickStarterService) - Sun Microsystems, Inc. - C:\Programmi\Java\jre6\bin\jqs.exe
O23 - Service: MSCSPTISRV - Sony Corporation - C:\Programmi\File comuni\Sony Shared\AVLib\MSCSPTISRV.exe
O23 - Service: NBService - Nero AG - C:\Programmi\Nero\Nero 7\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\Ahead\Lib\NMIndexingService.exe
O23 - Service: PACSPTISVR - Sony Corporation - C:\Programmi\File comuni\Sony Shared\AVLib\PACSPTISVR.exe
O23 - Service: ServiceLayer - Nokia. - C:\Programmi\PC Connectivity Solution\ServiceLayer.exe
O23 - Service: Sony SPTI Service (SPTISRV) - Sony Corporation - C:\Programmi\File comuni\Sony Shared\AVLib\SPTISRV.exe
O23 - Service: SonicStage SCSI Service (SSScsiSV) - Sony Corporation - C:\Programmi\File comuni\Sony Shared\AVLib\SSScsiSV.exe

--
End of file - 6727 bytes

Ciao lumauro .
Eccoti accontentato: il log è pulito.
Portalo in assistenza, visto che è ancora in garanzia.

Si tratta di un file che manca (è "svaporato", insomma, nel nulla). Il file scomparso era un BHO (Browser Helper Object), ossia un file il cui compito era quello di far da tramite fra il browser (Internet Explorer) e un qualche software "di terze parti"...