Although I agree with many of these answers - I would like to address the reasoning for re-imaging the machines in the first place and provide one more solution you perhaps have not thought about.
Microsoft (Windows) has a couple of programs that could make things a lot simpler for you to ensure the same experience of a clean image is given every time someone signs into the machine.
One of them which you should consider first is Microsofts (Built In) PC SafeGuard.
How to set up PC Safeguard:
1. Click to open Manage Accounts. ? If you are prompted for an administrator password or confirmation, type the password or provide confirmation.
2. Click the user account picture for the account you want to change.
3. Click Set up PC Safeguard. If you are prompted for an administrator password or confirmation, type the password or provide confirmation.
4. Click Turn on PC Safeguard.
5. Click Apply.
Then I would consider utilizing GPO if this doesnt cut it for you and you would like to allow more functionality or personalizations:
http://technet.microsoft.com/en-us/library/gg176673(WS.10).aspx
Let me know what you think!