Pro With SP3 Won't Let Administrator Have Full Control

I recently purchased an HP 8530w laptop that came with an xp from Vista downgrade preinstalled. I foolishly let Windows update automatically update the OS using the Express mode. It downloaded and installed SP3 and several .NET framework patches. The laptop also came with HP Credential Manager installed. The problem I'm encountering is that even though I logon under an administrator account I can't delete files under any of the USers under documents and settings, including the administrator acciunts Everytime I try to delete a cookie, or remove some documents (under My Documents) the file management program (Explorer or PowerDesk, I use both) pauses and then shuts down, and creates an error message to send to Microsoft. In short the system will allow the administrator to administrate. Can't uninstall SP3 because it doesn't show up in Add/Remove Programs, and can't delete any of the .NET framework updates even though they are listed.