use avira antivirus.its free and capable too.
once your system is virus free ,take these steps to avoid viruses from your system
1.insert the removable media.
2.go to my computer and get the drive icon.(eg. g:) **don't hit on the drive icon**
3.go to command prompt typing cmd in run box.
4.type drive icon: (eg. g:) to goto that drive.
5.type autorun.inf and press enter,,if a notepad opens there is a virus(most probably)
6. type attrib -s -h -r autorun.inf and press enter
7. type del autorun.inf
8. now open your drive typing drive icon: in run box.
9.treat files carefully and all folders icon are never folders only.check its property before opening.if its a file folder,,its ok.if program,dont open ,,,its a virus.simply delete it