Also, I advise if go with an XP or Vista machine, just use good judgement when you decide to set them up in terms of software.

Keep the additional programs to a minimum, run your Windows-updates, and use a good safe browser like FireFox or Safari. Do not use Internet Explorer, and avoid installing junk.

If the units come with any manufacturer-specific crap, format the drives with a legit copy of Windows and then run all updates and then install Jepp. This will make your system more reliable.

Good luck.