Vista has a significantly different kernel (nitty gritty core part of Windows under the covers), so it requires a good many new drivers. There're also programs that run under XP that don't run any more under Vista, so be sure to run the Vista Upgrade Advisor to find out about those. One I know of for sure is your antivirus software. Another thing is there is no OE in Vista, there's Windows Mail. The good news about Windows Mail is it's pretty much the same as OE, but you may have to save your contacts and emails and reload them, so check on that.
From a hardware point of view you'll want to be sure you have enough RAM. You'd probably want around 3 GB for Vista whereas XP would run pretty well in 1 GB. RAM's cheap, but be prepared to deal with that.
Now I don't know if you're aware of this, but you could upgrade to Windows 7 from XP. I assume you're thinking Vista because you already have it and don't want to spend another $100 or so for Windows 7. There're not that many folks running Vista these days, and it never had a good reputation. I think it's OK these days but you should at least be aware of Windows 7. Certainly if you want a 64 bit version, Windows 7 would be highly preferable.
I purchased my Dell desktop about four years ago and it came with xp and vista os. I loaded up xp. I'd like to now switch it over to vista so that I can upgrade to newer OSs from Vista.
Can anyone tell me how to do this and also advise as to what will happen to all my settings/docs/other apps. (or link me to instructions)
One more question, My outlook express has been acting weird (not showing messages - just headers) so I'm wondering if the switch over will also reintstall OE and IE. And how to save my emails and favorites.