Hi,
Method 1:
Step 1:
Check for the issue in ‘Safe Mode with Networking’.
‘Safe Mode with Networking’ starts Windows in safe mode and includes the network drivers and services needed to access the Internet or other computers on your network.
Access the below link to know more about ‘Safe Mode with Networking’:
http://windows.microsoft.com/en-US/windows-vista/Advanced-startup-options-including-safe-mode
Step 2:
If the issue doesn’t persist in safe mode, I would suggest you to perform clean boot and check.
Place the computer in a clean boot state and then check if it helps. You can start Windows by using a minimal set of drivers
and startup programs. This kind of startup is known as a "clean boot." A clean boot helps eliminate software conflicts.
How to troubleshoot a problem by performing a clean boot in Windows Vista or in Windows 7
http://support.microsoft.com/kb/929135
Note: After troubleshooting, make sure the computer to start as usual as mentioned in Step 7 in the above KB article.
Method 2:
I would suggest you to download and install Microsoft safety scanner and run the scan and check.
http://www.microsoft.com/security/scanner/en-us/default.aspx
Note: The Microsoft Safety Scanner expires 10 days after being downloaded. To rerun a scan with the latest anti-malware
definitions, download and run the Microsoft Safety Scanner again.
Note: Any data files
that are infected may only be cleaned by deleting the file entirely, which means there is a potential for data loss.