^^ I agree with RedGT, HP's have always had a tendancy to crap out pretty quick for whatever reason. Your issues verywell may be hardware more than Vista itself. (no hate intended)

That said, So far, I have had Zero problems with Vista, just be sure to get the latest updates b/c the initial version was full of bugs.
Also, since you had a Dell for 4 years w/out incident, and you decide to go back to a PC, just get a Dell.
I have no experience with Mac, so I have no opinion there.