Haven't tried version 3.91 (neither other versions) on XP, but maybe better use the latest stable version 3.90. This version has been released on 21st december 2001 and as far I now it works also OK for XP.
Using beta's often involves some risks...especially after a stable release because of a lot new stuff, which was post-poned due to the coming stable release.

Hopes this helps,

Eize