Try Prestageing the client computer twice, once for each user. I'm not sure it will let you use the sam GUID twice, but here is how to try what you are asking.
1.On the RIS server Click Start, point to Programs, point to Administrative Tools, then click Active Directory Users And Computers.
2.In the console tree, right-click the applicable OU that will contain the new client computer, click New, then click Computer.
3.In the New Object-Computer dialog box type the client computer name,authorize domain join permissions for the user or security group containing the user that will receive the physical computer this computer account represents, then click Next.
4.In the Managed dialog box click "This Is A Managed Computer", type the client computer GUID into the text entry field, then click Next.
5.Select your RIS sever.
The manufacturer supplies the computer's GUID. The GUID must be in the form {dddddddd-dddd-dddd-dddd-dddddddddddd}, where d is a hexadecimal text digit. For example: 8 hexadecimal text digits, followed by 4, then 4, then 4, then 12, such as the following: {921FB974-ED42-11BE-BACD-00AA0057B223}
Valid entries for the client GUID are restricted to the following:
0 1 2 3 4 5 6 7 8 9 a b c d e f -A B C D E F
Dashes are optional and spaces are ignored. Brackets {} must be included.
