The usual remedy for access denied is to take ownership of the folders and files. Google for XP TAKE OWNERSHIP and you'll find ample help.
Please note the sentence about booting in Safe Mode if you don't have XP Pro. Some people overlook it and come back complaining.
I was attempting to clear out my Temp and Cookie folders... a thorough clean out. Well... I un-hid my files and folders and disabled the hiding of the system files to get to the hidden temp and cookie folders. I tried to go to X:/documents and settings/ and my access is denied... I'm quite positive I'm the administrator account yet I don't have access to a lot of hidden folders.
*update* I am the admin account