PWD_2k.sys

My PC stopped with the error message: File pwd_2k.sys corrupt. Unable to continue.
I did not create this file, but it appears to be similiar to the PWD file used in Win 98, etc, for selecting a windows password.
Having disabled the file, windows boots up O.K. Some drivers,however, mainly CDROM drivers, are not being loaded.
How can I rectify this? And what is pdw_2K.sys.