The default NTFS permissions on the drive root, is Everyone with Full Control.

If you modify these permissions to tighten security, you must add the System account with Full Control and the Administrator account with at least Change. Everyone should have a minimum of Read on the drive root.

Failure to do so will result in the loss of full paging file functionality.

See tip 2733 (Windows 2000), tip 1767, and tip 1394.