there is one way i have been able to resolve this problem (it is not the best, trust me)

my office has over 70 computers with oses ranging from win 98 to win xp sp2.

what i did was create a server module which would record which user has logged into which computer. this is done by having a small client sending information to the server module on logon. this way, i was able to trace who was logged in where.