I just got an Axim X51v and found it only had two types of memory - Storage and Program which is quite different from my WM2003 Axim X3i...

With my Axim X3i, I had Main Memory as well as Built-In Memory. And when I ran programs, it took up memory on Main but you can also allocate storage space on Main...

So how has this WM5 changed? Can I install programs into Memory or will it always install into Storage?

Yes, read here:
http://www.aximsite.com/boards/showthread.php?t=102947