Hi,
Firstly, try to login with another administrator account to see if the files can be deleted. As a temporary workaround, you can also try to delete the files in Safe Mode or use the command line.
To solve this issue finally, try the methods below. If the previous method worked, no need to run the rest ones.
1. Use the Error-checking tool to check the volume for errors.
2. Use System Restore to to restore the computer's system files to an ealier and proper point.
3. Reboot the computer from a Windows Vista DVD and run Startup Repair to fix the system problem.
Hope it helps.
