Vista & Old Linksys Router - Wireless Problem?

I have a Linksys BEFW11S4 wireless router, which is 6 year old. The router
performs flawlessly with my XP machines. I bought a new Toshiba notebook w/
Vista and couldn't get the wireless connection to work properly (read: ultra
slow). After googling, I found some posts that the old Linksys is not
compatible with Vista and Linksys's web site doesn't include it as a
vista-compatible router.

So, is it true that old routers are not compatible with Vista? How can a
router be incompatible with an O/S???