Wall Street Journal's tech columnist Walter Mossberg is doing their Annual Buying Guide and put together a feature on how to tell if the new computer you're getting this spring will be be able to run Microsoft's Vista operating system, due out next January. He points out that just because machines on the market now have Vista Capable stickers on them doesn't mean they'll actually be able to run Vista proper:
If you have a computer with the weaker specs, Vista will still give you enhanced security and built-in desktop search. But you won't get the dramatic new graphical look and feel that makes Vista look more like the Mac OS. Your computer will look like an evolved version of Windows XP, and it will probably run only the wimpiest edition of Vista, called Home Basic.
His basic advice: get a Mac or wait till next year to get a PC with Vista on it. If you have to get a machine now, Mossberg lists the sets of specs you'll need to run Home Basic and full Vista.