Personally i wish windows 7 was 64bit only. Its time to ditch full on 32bit, seriously. On Vista 64 ive had no issues running 32 bit applications.
Only certain businesses have any purpose for not running 64bit, and well... they dont need the latest and greatest then because obviously they are using something super old. Either update your code, as its probably about damn well time you did, or keep using windows xp and complaining about vista (even though vista is perfectly good).
If anything couldn't run on 32bit compatibility its too fregin old, update your code or find a newer version, or find a replacement thats probably 100 times better.
sure you can "get" more then 4gb of ram on 32bit through this.... but WHY bother. Just install 64bit. Afterall, windows licenses aren't dependent on 32 vs 64, they just are for versions. So a "32bit vista ultimate" key is also a 64bit vista ultimate key. Etc etc etc. All you need to get is the like 5 dollar cd for 64bit os install. Microsoft does this as a way to encourage people to make the move over to 64bit.
My school only had 32bit media offered to us for the os's we could get cheap (vista ultimate being one of them), and i got ultimate and its key, then i went online and bought the 64bit cd to install it. wallah.
/sigh... at least we can almost safely assume that windows 7 is the last 32bit microsoft os.
Oh, and PG had a great way of explaining it with the kid counting. Kinda works well since its also super easy to count in binary on fingers