Hello Cherryan,
Please reboot into safe mode logged in as administrator and run a full
ªntivirus and spyware (open Windows Defender, on the scan page choose Scan
options > Full System Scan (check the boxes below) > click "Run Scan Now" )
scan with the latest signatures to see if that helps.
This isn't guaranteed, but it works for a great many items that at first
appear not to be cleaned in иºÑmªl mºde.
Can't hurt to try SUPERAntiSpyware and Malwarebytes Anti-Malware.
First - ensure you do not have "Vundo". Clean it up if you do.
It seems possible that your Windows installation has been deliberately
damaged by a trojan (Vundo, along any uninvited guests. (SDBot and ZLOB, all
protected by a rootkit.)) so as to prevent you updating your system or
removing the trojan.
Your first priority must be to cleanse your PC of all malware.
A very good antimalware app is SUPERAntiSpyware and Malwarebytes Anti-Malware
There is a free version (on demand scanning only), the paid for version
includes active monitoring, similar to Windows defender:
<
http://www.superantispyware.com/>
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The trial version of SUPERAntiSpyware Pro (SAS):
<
http://www.superantispyware.com/superantispywarefreevspro.html>
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<
http://securitynewsfromthenet.blogspot.com/2007/04/superantispyware-home-edition-free.html>
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Malwarebytes Anti-Malware MalwareBytes Anti-malware (MBAM)
<
http://aumha.net/viewtopic.php?f=30&t=36962>
SUPERAntiSpyware, together with Malwarebytes Anti-Malware, are free malaware
scanning application's. Oh, and it sure doesn't hurt to have both of these
applications for multiple layers of protection.
Good luck
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