<p><strong>Environment:</strong><br/>
Windows Server 2003 R2 Enterprise 64bit, SP2<br/>
.NET framework is supposedly installed (2.0 SP2, 3.0 SP2, 3.5 SP1)</p>

<p>I say "supposedly" because they are listed as installed under Add/Remove programs. I'm not sure it's <em>properly</em> installed, because the "ASP.NET" tab isn't added to any of the sites in IIS.</p>

<p>In the IIS Web Service Extensions section, I have both "ASP.NET v2.0.50727" (Allowed), and "ASP.NET v2.0.50727 (32-bit)" (Prohibited).</p>

<p>The site in question has script-execute enabled.</p>

<p><strong>Problem:</strong></p>

<p>I created a super-simple ASP.NET/C# website: Default.aspx with a label id="Label1", and a code-behind with: <code>Label1.text = "Hello World";</code> and the error I'm getting is:</p>

<blockquote>
  <p>%1 is not a valid Win32 application.</p>
</blockquote>

Have you tried running:
```
```
aspnet_regiis -i
```
```
from the command line?