Update 6 May 2010: Hello! If you're reading this, it's now at least 2010, and the answer to your question is: the version of ISA Server that works on Windows 2008 is called Microsoft Forefront Threat Management Gateway 2010. Also, it's exclusively 64-bit. ISA 2006 doesn't have a 64-bit flavour (though the Firewall Client does).
Yuri’s blog explains some of the detail. But there’s slightly more subtlety to it, which I’ll try to snake-oil in front of you here:
Can I install ISA 2006 on 32-bit Windows Server 2008 ?
No, it only runs on Windows Server 2003. Okay, so technically, it also runs on Windows 2000, but if you’re installing it like that now, you should check the calendar. Windows 2000 is old, man.
Why not ISA Server 2006 on Windows 2008?
Whenever I asked that, people mumbled about TCP/IP stack changes. Sounds plausible, so I let it slide.
Well can I install ISA 2006 on 64-bit Windows Server 2008 ?
No. Wait – sort of, not really. Do you count virtualization?
What do you mean?
Hyper-V or an SVVP-validated platform. (Details on security. And the inimitable “Jim Harris” apparently pretending to be Jim Harrison. Giggle.)
Er, if I do count virtual machines?
Yes. You run it in a 32-bit Windows Server 2003 guest.
Isn’t that cheating?!
No. Well, maybe. Sorry, did you have a point there?
What about Windows Server 2003, x64 Edition?
Installing ISA on it? No. It’s 32-bit only and uses kernel-mode software; you can’t mix and match 32-bit with 64-bit k-mode drivers. Hint: I just helped you study for 070-351.
What about Service Pack 2?
You’re not being helpful.
Oh really? Your eyes are the wrong shape.
The next version of ISA Server, called Forefront Threat Management Gateway (TMG, or, I guess, Timmy to his friends (yep, I’m betting the G ends up semi-silent)), is available in its initial release in the Windows 2008 Essential Business Server thingo, which is 64-bit only.
The next standalone (i.e. non-EBS-integrated) release is currently available in Beta form, and runs exclusively on Windows Server 2008, x64 edition.
That was more helpful.
You still look funny.
Hey, why don’t your links open in new windows?
Because I think it’s nice for the reader to be able to choose whether an informational link should appear in the current frame or a new tab (or a new window).
Sometimes (probably quite often on this blog), you’ll be done with the content at the current page you’re reading, and just want to replace it with something else. Forcing a new window isn’t polite in the age of tabbed browsing.
Let the user choose.
I agree, that’s so wise. You’re like, amazing.