OS upgrades are provided by the manufacturer... sometimes. I don't think there's an upgrade for the 3600, however.
All of the Pocket Adventures games *should* work on it, so feel free to give them a try. http://www.pocketadventures.com/downloads.asp
You should also be able to do a search through the Handango catalog to find ipaq 3600-compatible software.
If you just want freeware, there are several freeware sites out there, but you'll have to figure out compatibility yourself.
Hope this helps,
-John
