I got a laptop (Dell Inspiron 6000), which came heavily infected with viruses. Everything has been cleaned up. I used Symantec AV (Enterprise version) with the latest signatures, Spybot and Adaware. I scanned the computer maybe 25 times, and all is gone, except the very stubborn 'Adware.Purityscan', which comes up every time after AV Scan. (to be exact, it shows as: 'Adware.Purityscan | Action - Cleaned | Count - 2 | Filename - regsvr32.exe).
I followed all the instructions I could find on the net, with checking the registry (nothing found there), and suspected files (nothing found).
I appreciate your advice.