In past few weeks, one computer has become very slow in its internet interaction for downloads, mail, or other signed activity and secure sites. In fact, while I had run multiple internet windows (IE7), now only one window can operate to completely open (any second window will be "waiting to load" for prolonged periods, or not open at all). The connection speed still says 100 Mbps.
I ran new spyware programs downloaded to another computer (PCTools with antivirus first which did find numerous problems and Desktop Maestro), then CCleaner, and finally Norton 360, which found only a few additional low risk problems. I was unable to update these programs due to the download problem (efforts always failed), but presumably these are not too out of date, since they were run the same day they were downloaded.
I also tried reinstalling IE7, but that had no effect. I don't think it is the browser in any case since I tried a new installation of Firefox, and it behaves the same way.
I'm concerned about a hijacking program or other malware causing this issue, but it does not seem to be detected as above.
Suggestions?
Thanks.

