Should ASP.NET v2 IIS server extension be missing after .NET 4 is installed

I've run into this exact issue several times, and every time, the solution was to:

1. go to the Control Panel
2. go to the "Windows Components" area
3. remove IIS, let it uninstall
4. reboot
5. re-add IIS (make sure to include the ASP.NET stuff when you check off the boxes).
6. Run: C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727>aspnet_regiis.exe -I

I spent hours debugging this at a client site once, and that was the trick. Since then, every time this has happened, this was the fix.

I'm not sure what the root cause is, but we tore the IIS configuration apart once trying to figure it out, and even had Microsoft RDC'ing into the server in question for 2 or 3 hours, and they couldn't help either.

So I write it off as an undocumented bug in ASP.NET/IIS.

There are various things to check when asp.net starts acting all funky. Checking to make sure the extensions are allowed is one, though you usually end up getting 404 not found errors rather than other sorts of failures (this is an intentionally bogus error designed to avoid leaking information to potential hackers).

However, most sorts of troubleshooting eventualy come down to reinstalling the .NET Framework and then running aspnet_regiis.exe to reset everything. There shouldn't be any differences between IIS on 2k3EE vs 2k3SE.

Also, remember that IIS isn't PAE-aware so even if you do have tons of RAM on your box, you might still have problems taking advantage of it in any given app pool.