When it was supported, OE came bundled with IE. OE has long been
unsupported. It is a dead program. The last program updates were back in
2002 with one later functional change in SP-2 for Windows XP to add registry
hacks for top/bottom-posting and signature placement. The development team
was disbanded in 2006. You cannot get OE separately from IE. They came
bundled together. As of IE7 and later, OE is no longer bundled with IE.
IE6 was the last version that bundled OE with it. Microsoft is not going to
bundle unsupported products with supported products.
Windows XP comes with IE6 as its baseline version hence why OE is available.
Vista comes with IE7 and Windows 7 comes with IE8 as their baseline versions
of that web browser. You cannot install earlier versions of IE on those
Windows platforms.
You could run VirtualPC, VMWare Server, VirtualBox, or other virtual machine
managers (VMMs) on Vista and then install a pre-Vista version of Windows in
a virtual machine (VM) to have OE running inside that virtual machine. That
requires installing the VMM, installing pre-Vista Windows in a virtual
machine (VM), and then load that VM when you want to run OE. According to
Microsoft's EULAs, you will need another license of Windows to run it inside
a VM. That is a lot of work and nuisance to run a long-dead e-mail client.
For Windows 7, a license of Windows XP SP-3 in included called XP Mode. If
you install XP Mode and then VirtualPC 2007, you will have Windows XP
available inside a VM which comes with a baseline version of IE6 so OE6 will
be available; see http://preview.tinyurl.com/Win7xpmode-IE6OE6.
Note: Windows 7's XP Mode had required the CPU to support hardware-
assisted virtualization (http://preview.tinyurl.com/wiki-CPUvm).
Microsoft removed this limitation and now permits XP Mode to use software-
based virtualization (http://preview.tinyurl.com/XPmode-noHdweReq). Some
VMMs will run faster using their own software code than the virtualization
extensions added to the CPU (e.g., VirtualBox); however, VirtualPC 2007 is
not so blessed. A guest OS running in a VM is significantly slower than
the host OS and software-based VMs are slower than hardware-assisted VMs.
Windows Mail (WM) is the e-mail client included in Windows Vista. Windows
*Live* Mail (WLM) is the replacement for both OE and WM. Windows 7 does not
come with an e-mail client pre-installed so you will have to install one.
For WLM:
http://download.live.com
After installing just WLM, go into Add/Remove Programs and uninstall the
unwanted extra fluff software that Microsoft pushes onto you, like the
SignOn Assistant. While WLM is reminiscent of OE, it has some functional
differences. For help, the WLM newsgroup is at:
microsoft.public.windows.live.mail.desktop
There are plenty of other e-mail clients available, some of which are free,
like Thunderbird (and a derivative called Sunbird), or PIM programs that
have an e-mail functions, like EssentialPIM. You'll have to decide what
e-mail client you want to use under Windows 7 since that OS does not include
one.