While trying to install Windows SharePoint Server 2007 on a Windows Server 2003 machine (which had ASP.Net 2 SP 2 installed) I received an error that said ASP.net needs to be set to allowed in the IIS web extentions list of extensions. In fact, ASP.Net wasn't listed at all, let alone being able to enable it.

To get round this issue, I ran the following commands:

cd C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727
aspnet_regiis -u 
C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727>aspnet_regiis -i

The error indicates that IIS is in 64-bit mode, while this application is a 32 bit application and thus not compatible.

I assume that ASP.Net 2 (32-bit) had been installed, so uninstalled it and re-installed ASP.Net (64-bit), available from the Microsoft website.

I was unable to install Asp.Net 2.0 (x64) as I got:

Setup cannot continue because this version of the .NET Framework is incompatible with a previosuly installed one. For more information, seehttp://support.microsoft.com/support/kb/article/q312/5/00.asp
Microsoft .NET Framework 2.0 Service Pack 2 cannot be uninstalled because it will affect other applications that are installed. For more information, see http://go.microsoft.com/fwlink/?LinkId=91126

I then uninstalled (in this order):

SQL Server 2005
Application Server Component (incl. IIS)
ASP.Net 3.5 SP 1
ASP.Net

I may not have needed to uninstall SQL Server 2005 and IIS but after uninstalling those, it still wouldn't uninstall. I then came across a post that mentioned you had to uninstall the later version of ASP.Net.

I then installed IIS again, and ASP.Net 2 (x64).

I could then go in and allow the "ASP.Net v2.0.50727" web server extension.