If your logging on as Administrator then you should have access to all files and folders.
Go to Control panel,select files and folders click on the advanced tab and check the box show hidden files.
I still think that you need to do a repair install.It's the second repair option not the first,IE boot from CD with your win XP installation disc in the CD drive or DVD drive.
When it asks select install windows xp,it will then discover your present installation,then it will ask you if you want to repair this installation by pressing the R key ,press the R key.
It will then re-install windows.
Note: A repair install does not wipe your programs or data files,it just replaces missing or corrupt files for your system.So don't be afraid.
