Re-direct

I have a Win 7 home operating system and everytime I use my browser, I get redirected to a spam site. I used FireFox when the malware was downloaded and also have IE9 with the same issue.  I cannot get rid of this issue and have executed AV scans.  The malware does not show up on the AV scans. Is there anything I can do short of a reinstall?  Thank you.