mrmike49: Does higher level freeze spell work on vampires? That would seem the ideal way to avoid loss of stats.
If I remember correctly I used a freeze weapon, poisoned switching to lightening and back to the freezing sword. I can't remember how the freeze worked on him, I was a fairly high level when I finally killed him.
Vampires have a weakness to fire so fireballs work well against them or any fire weapon.
Here is a neat walk through of a wizard taking on the Vampire with fireballs. . . =)
Edit: it may take a minute to load this page since it has several images, you will need to scroll down a little to get to the vampire encounter.