I'm not basing my resource hungry allegations on what I've read or something...I'm saying these things based on more than a little experience with both OS's and, from my experience, Vista KILLS the same computer that XP would thrive on. Does this make it bad? No...not at all...if I hadn't have gotten a new pc early on as you spoke of, that had 512mb and was running Vista, the whole thing would have made more sense to me.
No matter what, my XP equipped Compaq has 256mb ram (it might have the 512mb the Vista equipped Dell struggled with...I don't remember off hand) and it still slaughtered the newer, fancier, possibly more powerful (I don't remember) Dell like a 1 legged deer on the call of open season...all this after bypassing the "immenent hard drive failure" screen at boot...lol Sure made me think of Vista as quite a greedy OS.