Grazie per la precedente risposta,
penso di aver risolto il problema. per maggiore sicurezza vi chiedo di esaminare il LOG.
ancora grazie.

Logfile of HijackThis v1.97.7
Scan saved at 23.43.23, on 05/10/05
Platform: Windows 98 SE (Win9x 4.10.2222A)
MSIE: Internet Explorer v6.00 SP1 (6.00.2800.1106)

Running processes:
C:\WINDOWS\SYSTEM\KERNEL32.DLL
C:\WINDOWS\SYSTEM\MSGSRV32.EXE
C:\WINDOWS\SYSTEM\MPREXE.EXE
C:\WINDOWS\SYSTEM\MSTASK.EXE
C:\PROGRAMMI\ALWIL SOFTWARE\AVAST4\ASHSERV.EXE
C:\WINDOWS\SYSTEM\mmtask.tsk
C:\WINDOWS\EXPLORER.EXE
C:\WINDOWS\SYSTEM\SYSTRAY.EXE
C:\WINDOWS\TASKMON.EXE
C:\WINDOWS\SYSTEM\STIMON.EXE
C:\WINDOWS\SYSTEM\SPOOL32.EXE
C:\WINDOWS\SYSTEM\E_S5I0C1.EXE
C:\PROGRAMMI\EPSON\EPSON CARDMONITOR\EPSON CARDMONITOR1.2.EXE
C:\WINDOWS\SYSTEM\WBEM\WINMGMT.EXE
C:\WINDOWS\SYSTEM\WMIEXE.EXE
C:\WINDOWS\SYSTEM\RPCSS.EXE
C:\WINDOWS\SYSTEM\RNAAPP.EXE
C:\WINDOWS\SYSTEM\TAPISRV.EXE
C:\PROGRAMMI\MOZILLA FIREFOX\FIREFOX.EXE
C:\PROGRAMMI\WINZIP\WINZIP32.EXE
C:\WINDOWS\TEMP\HIJACKTHIS.EXE

R1 - HKCU\Software\Microsoft\Internet Explorer\Main,Search Bar = http://server224.smartbotpro.net/7search/?new-hkcu
R0 - HKCU\Software\Microsoft\Internet Explorer\Main,Start Page = http://www.interfree.it/
R1 - HKLM\Software\Microsoft\Internet Explorer\Main,Search Bar = http://server224.smartbotpro.net/7search/?new-hklm
R0 - HKCU\Software\Microsoft\Internet Explorer\Toolbar,LinksFolderName = Collegamenti
O2 - BHO: (no name) - {A5366673-E8CA-11D3-9CD9-0090271D075B} - C:\PROGRAMMI\FLASHGET\JCCATCH.DLL
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: FlashGet Bar - {E0E899AB-F487-11D5-8D29-0050BA6940E3} - C:\PROGRAMMI\FLASHGET\FGIEBAR.DLL
O3 - Toolbar: &Radio - {8E718888-423F-11D2-876E-00A0C9082467} - C:\WINDOWS\SYSTEM\MSDXM.OCX
O4 - HKLM\..\Run: [SystemTray] SysTray.Exe
O4 - HKLM\..\Run: [TaskMonitor] C:\WINDOWS\taskmon.exe
O4 - HKLM\..\Run: [ScanRegistry] C:\WINDOWS\scanregw.exe /autorun
O4 - HKLM\..\Run: [EPSON Stylus Photo RX420 Series] C:\WINDOWS\SYSTEM\E_S5I0C1.EXE /P31 "EPSON Stylus Photo RX420 Series" /O5 "FILE:" /M "Stylus Photo RX420"
O4 - HKLM\..\Run: [StillImageMonitor] C:\WINDOWS\SYSTEM\STIMON.EXE
O4 - HKLM\..\Run: [TrojanScanner] C:\Programmi\Trojan Remover\Trjscan.exe
O4 - HKLM\..\Run: [SmcService] C:\PROGRA~1\SYGATE\SPF\SMC.EXE -startgui
O4 - HKLM\..\RunServices: [SchedulingAgent] mstask.exe
O4 - HKLM\..\RunServices: [LoadPowerProfile] Rundll32.exe powrprof.dll,LoadCurrentPwrScheme
O4 - HKLM\..\RunServices: [avast!] C:\Programmi\Alwil Software\Avast4\ashServ.exe
O4 - HKLM\..\RunServices: [SmcService] C:\PROGRAMMI\SYGATE\SPF\SMC.EXE
O4 - HKCU\..\Run: [EPSON Stylus Photo RX420 Series] C:\WINDOWS\SYSTEM\E_S5I0C1.EXE /P31 "EPSON Stylus Photo RX420 Series" /M "Stylus Photo RX420" /EF "HKCU"
O4 - Startup: Adobe Gamma Loader.exe.lnk = C:\Programmi\File comuni\Adobe\Calibration\Adobe Gamma Loader.exe
O4 - Startup: EPSON CardMonitor.lnk = C:\Programmi\epson\EPSON CardMonitor\EPSON CardMonitor1.2.exe
O8 - Extra context menu item: Scarica con FlashGet - C:\PROGRAMMI\FLASHGET\jc_link.htm
O8 - Extra context menu item: Scarica tutto con FlashGet - C:\PROGRAMMI\FLASHGET\jc_all.htm
O9 - Extra button: FlashGet (HKLM)
O9 - Extra 'Tools' menuitem: &FlashGet (HKLM)
O9 - Extra button: ICQ Pro (HKLM)
O9 - Extra 'Tools' menuitem: ICQ (HKLM)
O9 - Extra button: Translate (HKLM)
O9 - Extra 'Tools' menuitem: LingoWare Translator... (HKLM)
O9 - Extra 'Tools' menuitem: Sun Java Console (HKLM)
O16 - DPF: {D27CDB6E-AE6D-11CF-96B8-444553540000} (Shockwave Flash Object) - http://download.macromedia.com/pub/shockwave/cabs/flash/swflash.cab
O16 - DPF: {2BC66F54-93A8-11D3-BEB6-00105AA9B6AE} (Symantec AntiVirus scanner) - http://security.symantec.com/SSC/SharedContent/vc/bin/AvSniff.cab
O16 - DPF: {E77C0D62-882A-456F-AD8F-7C6C9569B8C7} (ActiveDataObj Class) - https://www-secure.symantec.com/region/it/techsupp/activedata/ActiveData.cab

conosci questo indirizzo?
http://server224.smartbotpro.net/7search/?new-hkcu

se non lo conosci devi eliminare le due righe

R1 - HKCU\Software\Microsoft\Internet Explorer\Main,Search Bar = http://server224.smartbotpro.net/7search/?new-hkcu
-
R1 - HKLM\Software\Microsoft\Internet Explorer\Main,Search Bar = http://server224.smartbotpro.net/7search/?new-hklm


Nel sistema manca un programma Firewall, installa questo
http://www.aiutamici.com/software/view.asp?tipo=home&CodSw=56


Fai un controllo antivirus da questo indirizzo
http://security.symantec.com/default.asp?productid=symhome&langid=it&venid=sym

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Collaboratore Aiutamici