NTUSER.DAT

Info

NTUSER.DAT files are the HKEY_CURRENT_USER hive for the registry an so they are integral part of the operating system and should be left alone.

One NTUSER.DAT for each user on the machine, some templates and repair.
C:\Documents and Settings\Administrator
C:\Documents and Settings\Default User
C:\Documents and Settings\LocalService
C:\Documents and Settings\NetworkService
C:\Documents and Settings\Your Name Here\NTUSER.DAT
C:\WINDOWS\repair
C:\WINDOWS\SYSTEM32\CONFIG\systemprofi...

An option to optimize your registry is NTREGOPT.

NTREGOPT - NT Registry Optimizer ERUNT - The Emergency Recovery Utility NT

http://www.larshederer.homepage.t-online...

Direct download links (the zip files just need unzipping and dropping on the drive.

http://aumha.org/downloads/erunt.zip
http://aumha.org/downloads/ntregopt.zip

Access

Your NTUSER.DAT is opened in regedit where it is available as HKEY_CURRENT_USER.

To access another user's file use "runas /user:Username regedt32"