I had a similar problem with my Pc. I took it to a small PC builder in Maidstone and he sorted it for me. Cost £35 but was money well spent as it breathed extra speed in to the PC. Cleaned up lots of rubbish, did not loose any data, and no more pop ups. He told me to Run Antuvirus, Spybot and AD-Aware every week. My probs had started when I up graded to Broadband and I forgot to switch the Microsoft firewall back on!