I am also searching for a way to get these drivers working in xp64, if I can;t find a way by monday I'm RMAing my 3rd card, I only have it so I can have SLi and a second monitor simultaneously - Ebuyer said naff all about 64biot support.
The annoying thing is there are drivers for xp 32 AND Linux 64bit but not windows 64bit.
I had an asus 9250 in my server machine, it came with 64 bit drivers on the cd.
Try searching the asus site for their version of the 9250 and you might find a driver, if I hadn't already sold my server machine i would just copy the cd and send it out to you but it's gone
Also the 9250 is not direct x 9 capable so there are no vi$ta drivers, you will have trouble in the future if you intend to migrate to vi$ta, there are a lot of direct x 9 cards out there for under 50 bucks.