Treo 270 help and info needed

I have a treo 270 that I got off my wife, she now has the 650. I was wondering where and what type of file goes onto this phone. I have downloaded several files that say they are jar file and jad files but none of these work. I have gone to some web sites that ofer free trial games and these files work. What type of file should I be using and is there a site that ofers free downloads for this phone? Also I would like to know how to delete programs from the phone that I have put on that dont work? Is there a way to upgrade your operating system on this ?