Under Windows 2000/XP you can set up accounts that have limited access, to prevent files from being modified or deleted, programs from being installed, certain documents from being accessed (tax returns, etc.) by certain users.
"i have manually deleted the files mentioned in the first error, this has no effect."
If you can manually delete the files, I would think the game should be able to.
"there are two users on this computer and we both are listed as computer admin (at least that what it says in the users accounts)"
Well, you can't get any more read/write access then that.
Did manually installing the game avoid the CRC errors you were getting?
I updated the CRC files listed in the
Troubleshooting and Manual Install Procedure topic to include the 1.34 patch, if you want to try that file verification method.