Windows XP Pro + SP2 is driving me crazy!

Hello,

I'm facing a strange problem (but I'm not alone) after install Service Pack 2 on my Windows XP Pro. After install it my computer becomes very very slow even to render the Google's main page.

I have found a lot of articles on Internet talking about this but everything they tried I have also tried without success.

I have tried several virus removal tools, anti-spywares and everything you can imagine!
Nothing happens, the computer continue to stay slow and slow...

If anyone have a hunch, please send it to me!!!