MSDN provides subscribers various versions of Windows 7 RTM. According to Microsoft, all features are actually installed, no matter which edition you have in hand. For example if you have Windows 7 Home Basic, you can upgrade to Ultimate without getting another DVD. The extra features will be unlocked from your computer.
Does that mean that all these ISOs are actually the same?
For Vista, MSDN provided one DVD that included Vista Home Basic, Home Premium, Business and Ultimate. With this DVD, the Vista edition that will be installed depends on the product key you entered in Setup.
But it is different this time. Installing from a Windows 7 Ultimate ISO, setup did not accept when I tried to put product keys from other editions.
Out of curiosity, I did a binary compare on two Windows 7 ISO - Home Premium and Ultimate. The two ISO have the same size - 2,501,894,144 bytes. And the difference was only 75 bytes.
I extracted the two ISO with WinRAR, both have 874 files and 200 folders. The total size was a little bit different. So I did comparison on all files with WinMerge. Turned out that the difference was only in one file - sources\ei.cfg. The contents of this file in Home Premium:
And in Ultimate:
So if you change only that file in the ISO, you do not need to download all editions. But the best solution is just delete ei.cfg, Setup will ask you which edition you want to install if it sees no such file.
With tools like PowerISO, one can delete files in a ISO. The following shows the steps to create a One-For-All-Windows-7 DVD that you can use to install Windows 7 Starter, Home Basic, Home Premium, Professional and Ultimate. I don't know about other tools, but I used PowerISO for this.
Step 0: Download one of the Windows 7 Edition (Starter, Home Basic, Home Premium, Professional or Ultimate). Note that Windows 7 Enterprise is not included in any of these ISOs.
Step 1: Open the ISO with PowerISO (or any ISO tool of your choice) and delete sources\ei.cfg
Step 2: Save the new ISO
Step 3: Burn the ISO or mount it.
Step 4: Try to install, you will see the following screen prompting "Select the operating system you want to install"
Will Microsoft eventually release a one-for-all Windows 7 ISO as in Vista? I certainly hope so, it will save many DVDs, covers and storage space.
On Testing Windows 7 in VMware Workstation
If you are installing Windows 7 using VMware Workstation, you don't need to modify the ISO, Setup will prompt you for the edition. I tested on VMware Workstation version 6.5.2 and although it treats Windows 7 as Windows Vista, the installation went fine. I suspect that Windows 7 Setup changes its behavior whenever it finds itself living inside a Matrix world. Or maybe VMware Workstation has a way to "ask" Windows 7 Setup to let you choose the Edition ?