I have an A8N SLi Deluxe based system running XP32 and Vista64. When using Vista the DVD drive is constantly spinning at full speed whether I use the drive or not, in XP the drive only spins when needed.

Is there a vista setting that determines this or is this maybe a driver issue - my ide controller or drive or something?

I cant see Vista needing the drive to spin 100% of the time.. It is Microsoft tho

It gets really hot so I can't leave a CD in the drive.

Maybe it is something to do with my anti virus or some vista search/index feature?

sounds like vista is thinking you DVD drive is a hard drive. How do you fix that? check the manufactuer for a fix, try reinstalling the drive with vista. The big thing with vista is that absolutely nothing was compatible at release and unless you buy it new there's no gurantee that it will ever be compatible. Thankfully you can get a good new DVD combo drive for under $40.