Vista - facing problem with virus attack

Hi All,
my system get infected with virus.
and that virus i don't know which type but
i fell that when ever i connect my system with internet, it automatically
fill my Hard disk space i don't know how but it happen.
few days back i have around 25GB space in my Hard Disk but now i have only
2.5GB Space.

when ever i open system it show one alert box and i don't remember the exact message but it show *abc.dll . fill infected. (* is any name).

please help for this problem.
and also tell me how can i get back the same space in the Hard disk.

please give me suggestion to get my system in orignal condition.

Thanks,
Manish Gupta

Mainish

There are several good anti virus apps but the only way you are going to be sure is to do a clean re-install. It will turn out to be faster, and better.

Let us know if you need help

Ken