Guys,
I had the same problem after ghosting a 160GB HDD to a 320GB HDD (ie, stuck at startup login screen). My original system disk was F: drive and after I did the ghost disk-to-disk the system could not see the F: drive, only the new drive sat as C:.
What I did was to use the following info from MS :-
http://support.microsoft.com/?kbid=223188
I did this using the Ultimate boot CD remote registry tool logged in as the administrator on the new C: drive disk and then changed the new disk to the F: drive again. Once I did this everything worrked fine with all my user accounts becoming available for login again.
I hope this helps.