Many a time while developing a web application you may come accross “Server application unavailable”

When you get this error in Windows XP make sure you have given ASPNET user sufficient rights on your physical application folder, it mainly requires read permission.

When you get this error in Windows 2003 server you can right click your virtual directory – permission – grant aspnet user sufficient rights there.

If the above solution doesn’t work here is another alternative,

You could try editing the Machine.config (located in
C:\WINDOWS\Microsoft.NET\Framework\v1.1.4322\CONFI G\).

Look for a key userName=”machine”. If you set it to “SYSTEM”
instead the aspnet_wp.exe runs with a different user (with
higher privileges).

Hope this helps

The .Net Framework has a feature called Shadow Copy.

Shadow copy is enabled on every appdomain created by ASP.NET by default. By default assemblies loaded will be copied to a shadow copy cache directory, and will be used from that location.

But this may create problem sometimes.