computer lagging

Hi, I'm on a Dell Inspiron e1505 running windows XP media center edition, and I've recently discovered that my computer is lagging. It started out as what I thought was only the sound, which is scratchy and skips often, but then realized that it was also video. I've now noticed that all programs are running slow. While the CPU usage usually rests low at 1-5%, it spikes, most often around 50% and many times around 70, 80, and 90% whenever a program opens, and if there is media playing, it skips violently then. The problem started promptly after I had been playing particularly loud music one day. I was not connected to the internet, and I fairly am sure that this is not a virus issue, as I have tested for spyware/malware/viruses, etc. It is also not bad RAM, as I have tested that. I also know that it isn't a speaker issue, as external speakers also skip (plus the accumulated other problems). I'm just confused… please help! –Chris

ive fixed the problem, so no need for responses… i cannot find out how to delete it though. if an admin could, that'd be great. thanks.

So what was the problem then?

i had to follow this: http://www.microsoft.com/whdc/device/storage/IDE-DMA.mspx