I need to run a .REG to add entries to the registry on logoff, but our GP environment disables regedit. I could probably accomplish this by turning regedit on, running the script, and then turning it back off again, but I'm hoping there's a more elegant solution than that.
Why not use a WMI script, run using cscript.exe.
Did you try REG.EXE?
REG.EXE allows you to do many Registry operations from a command line. This can be useful when you want to quickly make a change without opening RegEdit, and it also allows you to embed registry operations in logon scripts and batch files.
According to MS KB831787 Prevent Access to Registry Editing Tools policy changes in Windows XP and in Windows Server 2003 you can run regedit in silent mode, even on Windows XP/2003, if you update a GPO template.
From KB831787,