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2. According to one forum (I can't find now), Media Center functions are available in individual application on the Starter edition, they are just not conveniently bundled.

Home Basic is only available in emerging markets, where budgets might be a little bit tight. It does not include Aero, the glasslike user interface, or Windows Media Center. See Differences.

Windows 7 Enterprise will be sold through volume licensing to companies which have Software Assurance contract with Microsoft. It has features similar to Ultimate.

Source: Compare Windows - Microsoft Windows (Click "Featue Comparison Tab")
There is a more extensive Comparison Chart at Wikipedia.

Physical memory limits for Windows 7 versions

Version	32-bit	64-bit
Windows 7 Ultimate	4 GB	192 GB
Windows 7 Enterprise
Windows 7 Professional
Windows 7 Home Premium		16 GB
Windows 7 Home Basic		8 GB
Windows 7 Starter	2 GB	N/A

Prices of Windows 7
Full Versions of Home Premium

• Microsoft Store Online - Windows 7 Home Premium - 32 and 64 bit versions $200
• Amazon has 4 or more full versions of 64 bit Windows 7 Home Premium, plus upgrades from XP or Vista.
$110
• Microsoft Windows 7 Home Premium $180
• Home Premum 64 Bit System Builder (OEM) $100
• New Microsoft Windows 7 Home Premium 64-bit 1 PC License and Media PC from Adventurer's Bag * $142
• New Microsoft Windows 7 Home Premium PC * from Adventurer's Bag $263

See:
Windows 7 Installation Guide / Tutorial - Windows 7
Windows 7 Home Premium Setup at dmcritchie.mvps.org

OEM System Builder versions:
Almost everyone sells these OEM versions for around $100.
I am looking for a version to run on an Apple Macintosh, hence all the discussion about virtual machines and BootCamp, Apple's way to boot a Mac directly with windows.
The 64-bit version is recommended for Macs.

Amazon has a Windows 7 Home Premum 64 Bit System Builder for $100
B&H has a OEM version "licensed for distribution with a new PC" for $107

Ed Bott's Microsoft Report at ZDnet says,
"If you're building your own PC or looking for installation media that won't make you jump through hoops to install it, this product is extremely attractive, because it's significantly less expensive than a full retail license.
  The installation media works almost exactly like a full retail copy of Windows, except that it can't be used to perform upgrades, only a custom (clean) install. After installation, an OEM copy is essentially indistinguishable from a retail copy."

He quotes an answer from Microsoft engineers on their technical forum which says,
"The main difference between OEM and Retail is that the OEM license does not allow moving the OS to a different computer, once it is installed."

Thread at macrumors.com says, "Don't get the OEM version of you intend to switch back and forth between Bootcamp and Parallels or VMWare.

"The OEM version is meant to be installed on a "new" computer only. Our Macs don't technically qualify because we already bought them before we install Windows. OEM will install but MS doesn't approve and will happily revoke your activation and ability to use the product (without a refund) if they feel that you're violating the EULA or especially if the think you're trying multiple installs."

Using Windows in a virtual machine like Parallels appears differently to the Activation Scheme than Boot Camp does.

The best fix is to crack the Activation, but that's illegal. The Full Retail version allows you to remove from one computer and install on another. This would probably result in less of a hassle from MS.

I believe that Microsoft has said before, somewhere, that they are aware that the license can be interpreted to allow for installation on one's own system including a Mac, and they really don't care. For one thing, I believe they may make about twice as much money as they do off of a Dell, which isn't bad. But the trade-offs are that the installer of the software is responsible for support (that is, you are on your own) and you don't get transfer rights.