Dunno if this will confuse more, but the flyers at my door had this table.
Vista operating systems 1. Home basic $129 Can 2. Home premium $179 3. Business $249 4. Ultimate $299 Can.
-Most secure Windows with Wundows Defender and Firewall- 1, 2, 3, 4.
-Find what you need quickly with Instant Search and Internet Explorer 7- 1, 2, 3, 4.
-Elegant Windows Aero desktop with Windows Flip 3D navigation- 2, 3, 4
-Optimized for laptop with Windows Mobility Center and Tablet PC support- 2, 3, 4.
-Collaborate on and share documents with Windows Meeting Space- 2, 3, 4.
-Enjoy photos and entertainment with Media Center and enjoy Media Center on TVs throughout home via Xbox 360- 2, 4.
- Guard against hardware failure with advanced business backup features, enjoy better connectivity with Business Networking and more- 4, 5.
Protect data against loss or theft with Windows BitLocker Drive Encryption- 4.

No, I dunno what all that means. Looks like those who do photo work and play around with media need either 2 or 5.
Home Premium is provided with better PCs; Home Basic with the cheapies.

A similar table is given for the Office Systems (Ultimate-$700 Can).