> I was wondering if I could use my Palm Vx as a remote for my home theater system,
The answer is "maybe". I have a Palm Vx and the built in IR is not great. But you can try it and see how well it works for you. See below.
> and if yes, where/what software do I need to upload onto my Palm to do this.
Grab a trial copy of OmniRemote at www.pacificneotek.com
. Pardon the plug but you might also want to get a trial copy of ORDesktop at www.ordesktop.com
Try OmniRemote on your Vx and see if works for you. It might.