I'm about to do the same.
Just a word of warning. If your new machine has W7, be aware that Outlook Express, which I have been happily using on XP, is not supported by W7 and you will have to migrate to their horrid Windows Live Mail, (or Mozilla Thunderbird). I expect it is possible to export the stuff from OE to Live Mail but I'm paying someone £50/hour to do all this for me as I learnt a long time ago it's cheaper to pay a professional to get it right first time than to screw it up yourself.