Deploy an MIS by GPO but stop a reboot

Is there a way I can deploy a piece of software by GPO but stop it rebooting.
THe software deploys fine but as soon as it does it rebots the machine. Is there any way i can stop this? WOuld a .mst file do the trick and if so what would the contents be of the .mst file?

Can't you simply use the /norestart switch when invoking msiexec.exe?

If the installation needs to reboot the PC, why would you want to prevent it?

In the property table, add the REBOOT property with a value of ReallySuppress