Constant Not Responding And Very Slow!

Ok where to begin... My laptop had been playing up for some time now i ran antivirus programs through it. And done everything i could to try and get it working again... But with no luck! Unbearably slow constant freezing. So i decided to use Dariks boot and nuke and i reinstalled windows Xp this time Sp 3. I have a bit of a problem downloading the drivers but i got help from a very help full guy on here and i had sound etc! And.... Then it happened! After sorting out the drivers my laptop is now back to being really slow... Again i got avast security and numerous other programs but nothing comes up. It is unusable :( One thing i have noticed im not sure if this is the reason. In task manager... Processes... There is a process SVC HOST that is using 99 Cpu and that is making my Cpu at a constant 100%. If i end process well that does not help! I really hope some one can help me my make and model - Toshiba Satellite Pro L 10
Model Number: PSL15E-000801791


Thank you in advance.