It's not an Outlook Express issue.
Its holds the Windows user profiles.

"AK" wrote in message news:xQBxj.1161$TT4.5@attbi_s22...
: located in my "Owner" Directory:
:
: NTUSER.DAT 6.4MB
: also, ntuser.dat.LOG 1KB
: ---------------------
:
: WHAT IS THE PURPOSE OF THIS LARGE,IN-USE, FILE ON MY MAIN HARD DRIVE?
: I can't read these files because they are "in use by another process."
: Can they be deleted?
: AK
:
: