Good advice. I upgraded my PC as the laptop was unreliable, and chose Vista Premium. It is very good, with new features and helpful things. I don't think I would recommend you upgrade an older PC to Vista, as it is such a different program that you will have all sorts of problems getting things to work. Wait until you need a new one.
I specified that I wanted to be able to download analogue video from my camera. So they put in a video card. However, it would not pick up an audio. Tried umpteen things, phone calls, emails etc but no good. Finally read on the Internet that Vista was much more discerning with sound cards, and what worked with XP was not necessarily going to work with Vista. So I had to take the PC back to get a Vista certified sound card installed (the one they had put in wasn't certified-they just assumed it was OK as no-one else had complained). And then the audio pickup was fine.
That is the sort of problem you can expect as you are really mixing 2 technologies.