I have a 4 GB USB pen drive that I use with my Vista notebook for ready boost and data storage and it works fine. For ready boost I have allocated 1.5GB space.
But when I use the same pen drive with my XP desktop the Ready boost cache file disappears and I had to enable again it when I connect it to the Vista notebook. Is there a way to stop this from happening?

Note: I had to use the same pen drive with the Vista and XP computers because the other 4 GB stopped working.