you could also use something like a linksys WPG12 wireless presentation player, if your computer / palm has a wireless connection. It also includes a remote with a laser pointer.
more can be found at
http://www.linksys.com/products/prod...id=38&prid=503
they are in the ~$300 range, and with a wireless card for the computer as well, should come to way under the $500 budget