We're using the following VBscript code.  To test, save into a file with a .vbs extension and then run from a DOS prompt:
cscript.exe [yourfilename].vbs
It should output:
BIOS reported SN of Parallels-OB 12 34 45 56 78 90 12 23 34 45 56 67 78 89 90 
	
 I haven't tried to update the config file yet, but will test that shortly.  Also - is seems to preface the UUID with the text "Parallels" - is it possible to supress this text?
[Edit]  I'm having difficulty editing the the config file.  Using Finder (I'm working on a Mac), I right click the .pvm file and choose "Show Package Contents" which opens a new window containing the contents of the virtual machine.  I open up the config.pvs with my favorite editor (Smultron) and edit the <VmUuid> field with the value I would like to appear.  
When I boot the virutal machine, Parallels informs me that it (the virtual machine) is corrupt and gives me the option to remove.  I had to force kill Parallels in order to prevent it from "removing" the virtual machine.  I had saved a backup of the config file and restoring the copy made Parallels happy again.  Any advice as to how I should be doing this would be greatly appreciated.[Edit]
					 
				
			
			
			
		 
		
		
		
			
			
				Last edited: Dec 12, 2008