help

right computer(Xp) has a noticeable slow down really high cpu usage according to the little green box in the task bar with three firefox windows open it show 100% usage for a good while I only seen it at this for a few seconds before when running lots of programmes-gaming whilst scanning for viruses etc

I got great help last time I posted here so Ive come again theres something I have to down load I think

I havent been using the computer as of late as Ive bought a laptop but my sis has shes been using ie as opposed to me who uses firefox

ran avg last time as it was slow and found things (java/byteverify) I usually didnt find deleted them and this helped for a small while
now its back running avg anti-v, adaware and another adware software not finding anything so far

also in msconfig a lot of things in the services tab are marked stopped, including one marked essential remote procedure call locator?
there is also a nvcpl file running in start up that looks odd and I tapped it into google and is it a virus?

the avg has been showing kernal32.dll change for a while
and recently shell32.dll change, is this of any significance?

help anyone?
dont know much about computers but I thought I have been reasonably diligent
thanks