ancora grazie per il controllo log:

Logfile of HijackThis v1.99.1
Scan saved at 15.08.39, on 24/07/06
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\EXPLORER.EXE
C:\PROGRAMMI\HIJACKTHIS\HIJACKTHIS.EXE

R0 - HKCU\Software\Microsoft\Internet Explorer\Main,Start Page = http://www.virgilio.it/
R0 - HKCU\Software\Microsoft\Internet Explorer\Toolbar,LinksFolderName = Collegamenti
O2 - BHO: Yahoo! Toolbar Helper - {02478D38-C3F9-4EFB-9B51-7695ECA05670} - C:\PROGRAMMI\YAHOO!\COMPANION\INSTALLS\CPN\YT.DLL
O2 - BHO: AcroIEHlprObj Class - {06849E9F-C8D7-4D59-B87D-784B7D6BE0B3} - C:\PROGRAMMI\ADOBE\ACROBAT 5.0\READER\ACTIVEX\ACROIEHELPER.OCX
O3 - Toolbar: andRadio - {8E718888-423F-11D2-876E-00A0C9082467} - C:\WINDOWS\SYSTEM\MSDXM.OCX
O3 - Toolbar: Yahoo! Toolbar - {EF99BD32-C1FB-11D2-892F-0090271D4F88} - C:\PROGRAMMI\YAHOO!\COMPANION\INSTALLS\CPN\YT.DLL
O4 - HKLM\..\Run: [ScanRegistry] C:\WINDOWS\scanregw.exe /autorun
O4 - HKLM\..\Run: [TaskMonitor] C:\WINDOWS\taskmon.exe
O4 - HKLM\..\Run: [SystemTray] SysTray.Exe
O4 - HKLM\..\Run: [SoundFusion] RunDll32 cwcprops.cpl,CrystalControlWnd
O4 - HKLM\..\Run: [LoadPowerProfile] Rundll32.exe powrprof.dll,LoadCurrentPwrScheme
O4 - HKLM\..\Run: [avast! Web Scanner] C:\PROGRA~1\ALWILS~1\AVAST4\ASHWEBSV.EXE
O4 - HKLM\..\Run: [ashMaiSv] C:\PROGRA~1\ALWILS~1\AVAST4\ashmaisv.exe
O4 - HKLM\..\RunServices: [LoadPowerProfile] Rundll32.exe powrprof.dll,LoadCurrentPwrScheme
O4 - HKLM\..\RunServices: [Machine Debug Manager] C:\WINDOWS\SYSTEM\MDM.EXE
O4 - HKLM\..\RunServices: [avast!] C:\Programmi\Alwil Software\Avast4\ashServ.exe
O4 - HKLM\..\RunServices: [KB891711] C:\WINDOWS\SYSTEM\KB891711\KB891711.EXE
O4 - Startup: EPSON Status Monitor 3 Environment Check.lnk = C:\WINDOWS\SYSTEM\E_SRCV03.EXE
O9 - Extra button: Messenger - {FB5F1910-F110-11d2-BB9E-00C04F795683} - C:\Programmi\Messenger\MSMSGS.EXE
O9 - Extra 'Tools' menuitem: MSN Messenger Service - {FB5F1910-F110-11d2-BB9E-00C04F795683} - C:\Programmi\Messenger\MSMSGS.EXE
O9 - Extra button: (no name) - {85d1f590-48f4-11d9-9669-0800200c9a66} - :windir%\bdoscandel.exe (file missing)
O9 - Extra 'Tools' menuitem: Uninstall BitDefender Online Scanner v8 - {85d1f590-48f4-11d9-9669-0800200c9a66} - %windir%\bdoscandel.exe (file missing)
O16 - DPF: {644E432F-49D3-41A1-8DD5-E099162EEEC5} (Symantec RuFSI Utility Class) - http://security.symantec.com/sscv6/SharedContent/common/bin/cabsa.cab
O16 - DPF: {2BC66F54-93A8-11D3-BEB6-00105AA9B6AE} (Symantec AntiVirus scanner) - http://security.symantec.com/sscv6/SharedContent/vc/bin9x/AvSniff.cab
O16 - DPF: {9A9307A0-7DA4-4DAF-B042-5009F29E09E1} (ActiveScan Installer Class) - http://acs.pandasoftware.com/activescan/as5free/asinst.cab
O16 - DPF: {5D86DDB5-BDF9-441B-9E9E-D4730F4EE499} (BDSCANONLINE Control) - http://download.bitdefender.com/resources/scan8/oscan8.cab
O17 - HKLM\System\CCS\Services\VxD\MSTCP: NameServer = 192.168.10.100

è tutto pulito??? A me sembra di no??? che ne dite??? Grazie 1000

il log a parte questo è pulito , quindi metti la sua relativa spunta e premi su fix checked:
O4 - HKLM\..\Run: [SoundFusion] RunDll32 cwcprops.cpl,CrystalControlWnd

PS__assicurati che il tuo antivirus sia attivo e installa un firewall