I'd give you more precise advice if you had specified your Windows version and config, general tasks. etc.
Free virus removal software:
1 Avira Basic/Personal.
2. AVG Free.
3. avast! Home Edition (requires free registration).
4. Bit Defender Free.
5. PC Tools Free antivirus.
6. Malwarebyte's anti-malware.
8. EMSISOFT command-line anti-malware scanner.
There are free online virus scanners too, as noted by earlier replies. They can be of great help. I have a hub all about online scanners with links to those I tested.