DRM Error - Can't delete files in DRM folder

I've finally found the hidden folder C:\Documents and Settings\All Users\DRM
where my DRM files are found. In Tools - Folder Options I have 'show hidden
files' button highlighted but can't see the 15 files which 'properties' tells
me are in here. I also can't delete the file as I can't see it when I am one
step up in the All Users folder. The current ones are corrupted and I can't
use BBCiplayer or Channel4 OnDemand as it says my files are corrupted
Microsoft advice to delete these files and then restart WMP to renew my DRM
files. Can you help me solve this problem please as I've folled the Microsoft
advice and the links in this forum without any solution.
Cheers