HTC has just released the first official Windows Mobile 6.5 Upgrade for the HTC Touch Pro2, initially a Windows Mobile 6.1 device with promissed upgrade.
The update is a ROM update that will clear all data on your device and replace the current Operating System with the new one. Not much info on that, except for the fact that is is ROM version 1.86.401.0.
Download from the official HTC website, run the application and follow the instructions carefully!
Note: Make sure to backup contacts, emails, messages, call history.
Hint: use PIM Backup for all the above.