If you read through Microsoft’s…
How do I change the behavior of the User Account Control message?
…you’ll find that only Windows Vista Enterprise and Ultimate Edition users can change certain aspects of UAC for non-administrator accounts. This leaves out both the Home and Business Edition users out in the cold. This, IMHO, is just a bad idea and mystery to me. I also don’t understand why BitLocker wasn’t provided at least to Business Edition users (again Enterprise and Ultimate Editions have this feature). Why aren’t Business Edition users (at the very least) given these security related options?
BTW, if you want a good encryption option for Home or Business Editions, take a look at TrueCrypt 4.3a (released in May 2007). You may find it something you can use on PCs running that version of Windows.
Personally, I think Microsoft should follow Apple’s philosophy and just have a single edition and stop causing Edition Confusion.