Esegui 
ho letto ma non sò se ho fatto bene , di svuotare la cartella prefetch ( l'ho fatto ) e di cancellare i punti di ripristino ( non mi riesce ) anche se sono solo quelli che crea prima di installare un aggiornamento di windows update ( altri non ce ne sono ) .
allego il log di hijackthis :
Logfile of Trend Micro HijackThis v2.0.5
Scan saved at 09:52:23, on 30/08/2015
Platform: Windows 7 SP1 (WinNT 6.00.3505)
MSIE: Internet Explorer v11.0 (11.00.9600.17937)
Boot mode: Normal
Running processes:
C:\Windows\system32\taskhost.exe
C:\Windows\system32\Dwm.exe
C:\Windows\Explorer.EXE
C:\Program Files\AVG\AVG2015\avgui.exe
C:\Program Files\CCleaner\CCleaner.exe
C:\Program Files\Skype\Phone\Skype.exe
C:\Windows\system32\ctfmon.exe
C:\Windows\system32\GWX\GWX.exe
C:\Windows\system32\taskhost.exe
C:\Windows\system32\wuauclt.exe
C:\Users\wwxx\Downloads\HijackThis.exe
R1 - HKCU\Software\Microsoft\Internet Explorer\Main,Search Page = http://go.microsoft.com/fwlink/?LinkId=54896
R0 - HKCU\Software\Microsoft\Internet Explorer\Main,Start Page = https://mysearch.avg.com/?cid={DEA480C4-AA12-4FD6-90CC-45ED22A9B783}&mid=e78ab5bdfee547cdb3c2d16a1c1a59fe-bd71b1bed0c4d7d202a9104e8ee8cd869a63c41b&lang=it&ds=AVG&coid=avgtbavg&cmpid=0215pii&pr=fr&d=2015-03-13 22:00:43&v=4.1.4.948&pid=wtu&sg=&sap=hp
R1 - HKLM\Software\Microsoft\Internet Explorer\Main,Default_Page_URL = http://go.microsoft.com/fwlink/p/?LinkId=255141
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/p/?LinkId=255141
R0 - HKLM\Software\Microsoft\Internet Explorer\Search,SearchAssistant =
R0 - HKLM\Software\Microsoft\Internet Explorer\Search,CustomizeSearch =
R0 - HKCU\Software\Microsoft\Internet Explorer\Toolbar,LinksFolderName =
O2 - BHO: SkypeIEPluginBHO - {AE805869-2E5C-4ED4-8F7B-F1F7851A4497} - C:\Program Files\Skype\Toolbars\Internet Explorer\SkypeIEPlugin.dll
O4 - HKLM\..\Run: [AVG_UI] "C:\Program Files\AVG\AVG2015\avgui.exe" /TRAYONLY
O4 - HKCU\..\Run: [CCleaner Monitoring] "C:\Program Files\CCleaner\CCleaner.exe" /MONITOR
O4 - HKCU\..\Run: [Skype] "C:\Program Files\Skype\Phone\Skype.exe" /minimized /regrun
O4 - HKUS\S-1-5-19\..\Run: [Sidebar] %ProgramFiles%\Windows Sidebar\Sidebar.exe /autoRun (User 'SERVIZIO LOCALE')
O4 - HKUS\S-1-5-19\..\RunOnce: [mctadmin] C:\Windows\System32\mctadmin.exe (User 'SERVIZIO LOCALE')
O4 - HKUS\S-1-5-20\..\Run: [Sidebar] %ProgramFiles%\Windows Sidebar\Sidebar.exe /autoRun (User 'SERVIZIO DI RETE')
O4 - HKUS\S-1-5-20\..\RunOnce: [mctadmin] C:\Windows\System32\mctadmin.exe (User 'SERVIZIO DI RETE')
O9 - Extra button: Skype Click to Call settings - {898EA8C8-E7FF-479B-8935-AEC46303B9E5} - C:\Program Files\Skype\Toolbars\Internet Explorer\SkypeIEPlugin.dll
O11 - Options group: [ACCELERATED_GRAPHICS] Accelerated graphics
O18 - Protocol: skypec2c - {91774881-D725-4E58-B298-07617B9B86A8} - C:\Program Files\Skype\Toolbars\Internet Explorer\SkypeIEPlugin.dll
O23 - Service: SAS Core Service (!SASCORE) - SUPERAntiSpyware.com - C:\Program Files\SUPERAntiSpyware\SASCORE.EXE
O23 - Service: Adobe Flash Player Update Service (AdobeFlashPlayerUpdateSvc) - Adobe Systems Incorporated - C:\Windows\system32\Macromed\Flash\FlashPlayerUpdateService.exe
O23 - Service: AMD External Events Utility - AMD - C:\Windows\system32\atiesrxx.exe
O23 - Service: AVGIDSAgent - AVG Technologies CZ, s.r.o. - C:\Program Files\AVG\AVG2015\avgidsagent.exe
O23 - Service: AVG WatchDog (avgwd) - AVG Technologies CZ, s.r.o. - C:\Program Files\AVG\AVG2015\avgwdsvc.exe
O23 - Service: Servizio Google Update (gupdate) (gupdate) - Google Inc. - C:\Program Files\Google\Update\GoogleUpdate.exe
O23 - Service: Servizio Google Update (gupdatem) (gupdatem) - Google Inc. - C:\Program Files\Google\Update\GoogleUpdate.exe
O23 - Service: MBAMService - Malwarebytes Corporation - C:\Program Files\Malwarebytes Anti-Malware\mbamservice.exe
O23 - Service: Skype Updater (SkypeUpdate) - Skype Technologies - C:\Program Files\Skype\Updater\Updater.exe
--
End of file - 4003 bytes
Grazie mille a chi risponderà .
