I was working at a customers site last year creating a media based Windows 7 deployment for some laptops. I over heard one of the technical leads saying that he was deploying XP to a machine so he could use system information to collect the exact model from the machine. Naturally I offered him a quicker solution for which he was eternally grateful.
Boot into WinPE and type
WMIC csproduct list /format
This will display the Make, Model and UUID in a formated list collected from WMI. You can use this tool in XP through to Windows 7 and on server editions also. You can find a list of commands using the WMI Command-line Tool tool here.