No GUIDs need deleting, the Computer is identified by the console using the combination of Primary Keys you set in Tools > Options > Global. You have the choice of one or more of:
- MAC Address
- UUID (unique GUID like id that should be in most modern BIOSes)
- Serial Number
- Asset Tag
If you will be using more than one Deployment Server you might want to remove the Server name or IP address from HKLM\Software\Altiris\eXpress.