I got a T|T3 with ROM update, using Palm Desktop v4.14. Handheld was from about 3 years ago, while PD upgrade was recent. I'm assuming much hasn't changed since then to the versions of Hotsync, Palm Desktop, and Palm OS you're using.

You can set you're HS user name when u first HS on that handheld. On the desktop, choose an existing username or create a new one. After that, on the desktop, u can also edit a username and edit the name. HS-ing should also edit the name back on your handheld too. There is no direct way to put your username on a Palm. AFAIK, there are 3rd party utilities that can do this, but I can't remember any of them by name. I'll post back if i can remember any of them.