When I added my HTPC to my Harmony 659 remote, I added the device as a "Microsoft Windows XP Media Center 2005" and it found the correct codes for the Microsoft remote. I also just tried the following:
Computer->Media Center PC->Microsoft (as the PC manufacturer)->Media Remote 1039
and that worked too.
thanks .... i'm pretty sure i tried all that..but will do again when i get home later...i'll try the same text string you mention..