So, restating for future readers, it appears that set is retained in Win7, but the former (I think, right thru Vista) variant, setxwhich was required to set %PATHEXT% permanently, seems to have has been removed as of Win7.

but the former (I think, right thru Vista) variant, setx

Have you searched the system dirs for the executable? :

c:\>attrib /s %systemroot%\setx.exe
A            C:\Windows\System32\setx.exe
A            C:\Windows\SysWOW64\setx.exe
A            C:\Windows\winsxs\amd64_microsoft-windows-setx_31bf3856ad
+364e35_6.0.6000.16386_none_065eaf56d482c350\setx.exe
A            C:\Windows\winsxs\x86_microsoft-windows-setx_31bf3856ad36
+4e35_6.0.6000.16386_none_aa4013d31c25521a\setx.exe
[download]

Maybe it is still there, but not on the path for some reason?

which was required to set %PATHEXT% permanently, seems to have has been removed as of Win7.

You can also do that via the "Computer" icon on the desktop.

Right click and select "properties"->Advanced system settings->Environment variables->system variables->(scroll and select)PATHEXT->Edit->(change)->OK.

(Of course, the exact sequence has probably changed on Win7.)

Hardly convenient, but you only need do it once.

---

With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.

"Science is about questioning the status quo. Questioning authority".

In the absence of evidence, opinion is indistinguishable from prejudice.

The start of some sanity?

hmmm, apparently it's part of the documentation<replace>I failed to find it</replace> in the morass below technet that's disappeared but C:\>setx /? (which I should have also tried) is still extant and your search using ATTRIB also works (and is a revelation to /me).

C:\>attrib /s %systemroot%\setx.exe
A            C:\Windows\System32\setx.exe
A            C:\Windows\winsxs\x86_microsoft-windows-setx_31bf3856ad36
+4e35_6.1.7600.16385_none_ac4d2bf27a63f85f\setx.exe
[download]

The click-sequence for setting %PATHEXT% via COMPUTER (which is in START; I have already forgotten if I deleted the "My Computer" icon from my desktop or if was never there) has been, as you speculated, subject to a few revisions:
COMPUTER is however, now a default item in Win7|START, and works under Win7 as I outlined above
(Thanks, M$; do you do this deliberately to confuzelate the simpleminded, like /me?)

Update in the <strike...</replace> sequence