My Windows 7 logon time could be measured in minutes.  So I tidied up my Roaming Profile.  4GB of space savings later, I was removing the last of the files in the 5 to 20MB range.  One of these files was NTUSER.DAT.START.

NTUSER.DAT is a copy of the user’s HKCU registry settings and is used with Roaming Profiles.

But this NTUSER.DAT.START file?

As it turns out, it’s created by the Citrix UPM product.

NTUSER.DAT is read at profile load and we copy it to NTUSER.DAT.START.

At the end we compare NTUSER.DAT.START and end of session NTUSER.DAT and create a difference file called NTUSER.DAT.NET.

At logoff we merge the changes in NTUSER.DAT.NET (apart from exclusions) into the NTUSER.DAT on the network file share.
– Citrix Support Thread: NTUSER.DAT.NET, NTUSER.DAT.START

At logoff it supposed to be deleted.  In my case it wasn’t, and since I didn’t have any Citrix sessions running, I deleted it.