Brim:
Those systems will be running much faster than than your shiny new Vista O/S. There is absolutely no reason to upgrade from XP. In fact there are more reasons to downgrade from Vista.
When buying my latest Dell XPS M1530 laptop at the start of the year I was tempted to stick with XP, or to dual boot due to all the
horror stories.
But I have had
no problems with hardware or software compatability, and the XP operating system was soon forgotten.
I find Vista to be smooth, fast, responsive and stable, XP would be a backward step.
As I said, if upgrading you need to be certain that your PC is modern and capable of running Vista, do NOT believe the "Vista Capable" stickers
But for anybody who has recently purchased a new high spec PC, and mistakenly chose XP over Vista, this is a good deal.