There is a free GUID generator called GUIDMaker which has a scriptable component available here: http://www.serverobjects.com/products.htm

Download the small zip, extract the DLL, copy to your system32 directory and register it.

Once you've done that you can issue GUIDs to your heart's content.

Here's one I prepared earlier:
Code:
$sGUID=CreateObject("GuidMakr.GUID").GetGUID
"GUID="+$sGUID+@CRLF


Output:
Quote:

GUID={BA456FCA-FC6F-45D4-A72B-2C9DFAF07E89}