Can my HP Pavilion dv2000 run Windows Vista Ultimate?

No. With only half a gig of memory it probably doesn't run XP very well either. You also have one of the earliest Core2Duo processors, but that will be ok if you quadruple the amount of memory that it has. However, don't bother with Vista, go straight for 7 if you intend to do this - it's more efficient and will run better.