Problem running combofix

Howdy - I'm working my way through the read first stuff, and I'm into the vista cleaning guide now. I'm not able to get ComboFix to run. I downloaded it from the link in the guide, and I've completed all of the prior steps in the guide (and cleaned out a few trojans in the process), but when I try to run ComboFix, I get the following 2 errors:

---------------------------
Error - Win32 only
---------------------------
Incompatible OS. ComboFix only works for Windows 2000 and XP

<repeated in several languages>

and then:

[Window Title]
32788R22FWJFW\nircmd.com

[Content]
Windows cannot find '32788R22FWJFW\nircmd.com'. Make sure you typed the name correctly, and then try again.

[OK]

I think my system is clean now, but I'd stilll like to finish the guide. Any ideas?