I have moved to running Windows XP and am currently using Outlook Express Is it possible to transfer E mail messages I saved in pst file on my old machine onto the new machine

I don't really know, but logic will suggest either two things, if they are saved on a different server, than copy them, I don't know what the pst format is though :D. If they were just on your harddrive, they should be there if all you did was installed XP. Otherwise, copy them from back-up or if you never saved them and they were on your computer, they are gone...
Clearly I have no clue what I'm talking about...