Connecting to Windows 2003 via dos client

Hi We run a fairly big network using images to restore
machines and used to run NT servers previously i could
automatically image any machine on my network via an exec
utable which would restart the machine and then login to
nt share and store the image for use at a later
date,however since we upgraded to windows 2003 server this
procedure does not work for some reason,after reboot when
the machine tries to connect into the share via dos i get
a bad password error,the same user and password works in a
windows environment just fine can anyone shed any light on
this at all,if i have been vague in my information please
let me know

Embazzy