Windows 7 Versions / Editions Compared

Win 7 comes in many different flavours but in North America there are only 5.

Quick Notes:

If you are using Windows 7 Starter, about the only things you will find annoying is the inability to change wallpapers and that lack of Aero (the glass like window frames in 7)
Ultimate and Enterprise are the same product however Windows 7 Enterprise is a corporate license only SKU which allows the user to access some additional software like MDOP.
If you use Windows and your company has more than 5 people in it, you should skim THIS article which explains how to buy Windows Professional but get Windows Enterprise for no additional fees.

Below is a simple list of common Windows 7 Features:

Home Use Stuff	Starter	Home Premium	Professional	Ultimate/ Enterprise
32-bit and 64-bit versions	32-bit only	Both	Both	Both
Maximum physical memory	2GB	16 GB	192 GB	192 GB
Maximum physical CPUs supported	1	1	2	2
Maximum CPU Cores Supported	Unlimited	Unlimited	Unlimited	Unlimited
Backup and Restore Center	Cannot back up to network	Cannot back up to network	Yes	Yes
Multiple monitors	No	Yes	Yes	Yes
Fast user switching	No	Yes	Yes	Yes
Desktop Wallpaper Changeable	No	Yes	Yes	Yes
Desktop Window Manager	No	Yes	Yes	Yes
Windows Mobility Center	No	Yes	Yes	Yes
Windows Aero	No	Yes	Yes	Yes
Multitouch	No	Yes	Yes	Yes
Premium Games Included	No	Yes	Yes	Yes
Windows Media Center	No	Yes	Yes	Yes
Windows Media Player Remote Media Experience	No	Yes	Yes	Yes
Encrypting File System	No	No	Yes	Yes
Location Aware Printing	No	No	Yes	Yes
Remote Desktop Host	No	No	Yes	Yes
Presentation Mode	No	No	Yes	Yes
Home Group (create and join)	Join only	Yes	Yes	Yes

Corporate Stuff	Starter	Home Premium	Professional	Ultimate/ Enterprise
Windows Server domain joining	No	No	Yes	Yes
Windows XP Mode	No	No	Yes	Yes
Aero glass remoting	No	No	No	Yes
AppLocker	No	No	No	Yes
BitLocker Drive Encryption	No	No	No	Yes
BranchCache Distributed Cache	No	No	No	Yes
DirectAccess	No	No	No	Yes
Subsystem for Unix-based Applications	No	No	No	Yes
Multilingual User Interface Pack	No	No	No	Yes
Virtual Hard Disk Booting	No	No	No	Yes