Assistance but is this a virus spywRe?

My desktop pc seemsvto be struggling with connwcting to the internet. All other internet connections in the hoyse are working fine. The desktop pc says it is connected to my wireless at 54mps which is the usual speed. Yet every time i try to use it on internet either with internet explorer or safari, which i prefer, it won't do it and says it can't find server. I haven't downloaded or installed anything. I have run a complete virus scan plus two different malware finders and all has come up with zilch found.

This problem only started a couple of days ago. Occassionally it finds the internet but is so slow on loading pages and then hangs half way through loading a website anyone i pick and then says it can't find server again.

I am using xp media centre 2005 edition sp2 with all lates updates. did use sp3 but it screwed up my media centre so i had to get rid of that.

I've checked everything i can think of including ensuring under lan settings it is set to the auto bit.

It's leading me to believe something is on
My machine but i can't find it for love nor money.

Any advice greatly appreciated.