If I pick up a used Treo 750, which has Wince, ergh, WM5.x on it, can that be upgraded to a later version like WM 6.x?

I didn't see any mention of it as Palm's web site or MS's. Don't know if they consider that a new OS to buy (like Windows in general) or a firmware upgrade to give away. Or even if the phone can handle updated versions.

Anyone?

(Sorry, I'll be posting in the 750 section too, it is one and the same.)