You likely have a virus infection.
Use another PC to download Stinger.exe and save to a floppy disk.
Then copy it to the other PC and run it in Safe Mode.
If the PC keeps freezing you can pull out the HDD and attach it to another PC and scan with Stinger.exe.
Here is the link for Stinger:
Besides Stinger you should also scan with other tools in the Anti-Parasite suite:
everytime i start the computer it is slow then when i get into windows the start up tool bar frezzes help! plz
my e-mail is : firstname.lastname@example.org
or write in the fourm
i have windows xp pro.
pentium(R) 4 1.40GHz and 513 MB of ram