net use from XP Pro Client to NT4 Domain

I've set up some XP Pro Clients that are in Domain under a NT4 SP6a
Server.
Those clients seem to have problems when mounting a Servershare with
the "net use" command :
if I use the net.exe from XP I get allways a request for a password,
while if the net.exe is copied from the NT Server it works without a
problem, mor or less - the problem is that I cant replace the net.exe
on XP (I think some sort of autorepair function) so I use to have it
renamed to net2.exe
Is there some better solution ?
This way I have to check OS Version prior to connecting the shares.
T.i.a.

Georg