Windows 7 - Windows 7 on Windows XP.. not allowing domain logon

hi..
yesterday system administrator in my group installed Windows 7 on our PC(we share a single PC) which had XP earlier.. and this PC is on our University domain...issue is I can login to Windows 7 using the domain acccount.. but when I tried to login to XP, I receive a message saying that this system is not on the network or the domain is not available.. I logged in to XP using local account and can see that the system is hooked up to University domain, and both XP and Windows 7 versions have same computer name..........

what could be the reason for this???

Im unable to get in otuch with the admin who installed Windows 7, coz he works night shifts and another admin can't figure out..

Different Domain SID, one per machine name but they have the same name which is probably causing problems. When the admin installed and connect Windows 7 to the domain it registered its computer name to a Domain SID. But Windows XP has the same name but the Domain SID does not point to it.

Or something to that effect...don't quote me on it >.>

u r correct...problem was similar computer name on both OS... i gave diff names and all is well..thanks a lot