After about 10 min of normal running my computer slows down, how can I fix it?

After about 10 min of normal running my computer slows down exponentially, and I can't do anything at all. At that point it will take +5 minutes to close a window. In safe mode my computer runs fine, and I don't get this problem at all. I've run an updated Norton-Antivirus full system scan, as well as a Microsoft Defender system scan, both came up with nothing. P4 2.4 Ghz, 512 Ram, XP Pro SP2, Radeon 9600. I'm trying to avoid having to format my hard drive. What is this and/or how can I fix it?

After about 10 min of normal running my computer slows down, how can I fix it?norton internet security

check ur system tray,and close the un wanted programs runnig.

After about 10 min of normal running my computer slows down, how can I fix it?spyware remove

Do the following:

1.Empty the prefetch directory in C:\windows

2.in the Bios disable quick power on self test(POST)

3.Disable Boot up floppy seek

4.disable Boot delay in the bios if run into problems turn it back on.

5. click on internet tools and delete the cookies.

6.Perform disk cleanup, then Disk defragmenter and Chkdsk 1 to 5.

7.Change virtual memory to minimum 2096 and maximum 4096.