If you have worked your way through all the suggestions in Thread779-609362 and not found a solution, it is hard to think of what else to advise.
Are you having any other problems on your machine besides this one?
Are you fully updated with Service Pack 1 and Windows Updates?
Are there any error messages in your Event Viewer?
To check your drivers.
HOW TO: Verify Unsigned Device Drivers in Windows XP
To check conflicting software.
310353 - How to Perform a Clean Boot in Windows XP
316434 - HOW TO: Perform Advanced Clean-Boot Troubleshooting in Windows XP
Some general things to try.
A scan of your Registry with a reliable Registry Cleaner may help.
Try Safe Mode (Do you have this problem in Safe Mode?).
Try running ChkDsk to check your drive for errors. Right click your Drive icon/ Properties/ Tools/ Error Checking.
Run the System File Checker program from the Run Box by typing.....Sfc /Scannow in it and have your XP CD handy.
If they don't work you could try repairing windows itself by running it over itself. You will lose all your windows updates but your files will be untouched.
How to Perform an In-Place Upgrade (Reinstallation) of Windows XP (Q315341)