Are you running the dreaded Vista ?
Or, XP with Service Pack 3 ?
It may be a 'Security Center' issue... (A kind of virus from Microshaft !)
And, what player(s) are you running and what CODEC pack(s) ?
You may also be correct in your assumption that it could be a virus...
If so, try
Malwarebytes.org
Be sure to follow the install instructions and download it to your Desktop ONLY...
The program is free and completely safe.
You should also consider clicking on
Nod32 - Free Virus Scan: Use ESET's Online Antivirus Scanner
which is also free and completely safe.
These are the two best 'detectors', 'cleaners' and 'removers' I know of...
As for the second mentioned problem, please supply more detailed info...