[krohnjw]

For anyone tryting this in Windows 7 QPST will work - you do need the appropriate drivers though.

When you connect in Diag mode it will install the modem driver - however check device manager. You will likely see a Generic Serial device showing up. If that's there you'll need the driver (didn't install automatically or via windows' "search"). I've attached the WModem Installer below (32 and 64 bit).

After installing that it will create the HTC Diagnostic Interface (under Ports COM & LPT) with a new COM. That will be the COM you want to select in QPST and all should then work.