There may be a good reason they are not selling WM5 anymore.It didn't work very well on the X50.Some got it working but most didn't.Save your money and sanity and stick with what you have.Also welcome to Aximsite.
I have an X50v running WM2003SE. I have never bothered to upgrade to WM5. I've just found out that a piece of software that I use daily (a medical program - UpToDate) is going to require WM5. Am I screwed? Can I still get WM5?