Hmm. No PC is running fine. Yes, it has to be either your computer or your programs, ISP etc. Are you on dialup? What does it say the speed is now? I found when I was on dial up they consistently slowed the rate, pushing me into DSL. Of course.

Perhaps someone added a new program to your computer? I know when I loaded my speech program even onto this giant memory computer, it slowed it some.

Did you check and see how many processes you have running at one time? Someone may have added a program that runs "in the background" all the time.

Did someone set your virus software to constantly check? THAT is a huge slow downer (is that a word?)

I hope even if it's none of these things, that it helps you think of what it is. GOOD WISHES!