Hi, welcome to the forums.

Please Help us to Help you In order to help fully we need more information…
- What OS are you using? is it up to date?
- What avast! version and VPS file (virus database) number, e.g. 0436-4 (see about avast!)
- What was the virus name, what was the filename, where was it found
example (C:\windows\system32\infected-filename.xxx)?

If a program is in use and windows is protecting it, then it is difficult to get rid of it at the time. If you have w2k/XP you can schedule a boot-time scan in avast!

Advice & Tools for virus/trojan/malware Removal & Prevention