Gotta say - these days I think the best thing is to get the most generic gear you can and install an LTS mainstream Linux distro.
Pretty much my opinion too, except I say go buy the cheapest thing that suits you needs and requires the least amount of user input.
@maxed-out - your biggest problem putting win 7 on an older PC is the lack of drivers. Manufacturers of hardware tend not to go back and write new drivers for old hardware unless is very specialised stuff. If you want to upgrade, buy a cheap PC from Dell or your local chain computer store is probably a better way to go. Otherwise just stick with XP for now, which these days is fairly secure provided you dont go clicking on links in emails too often (or surfing for porn
).