I copied my portal to WIndows 2003 and now I am getting:

Server Error in '/portal' Application
--------------------------------------------------------------------------------

The current identity (NT AUTHORITY\NETWORK SERVICE) does not have write
access to 'C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\Temporary ASP.NET
Files'.
Description: An unhandled exception occurred during the execution of the
current web request. Please review the stack trace for more information about
the error and where it originated in the code.

Exception Details: System.Web.HttpException: The current identity (NT
AUTHORITY\NETWORK SERVICE) does not have write access to
'C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\Temporary ASP.NET Files'.

Source Error:

An unhandled exception was generated during the execution of the current web
request. Information regarding the origin and location of the exception can
be identified using the exception stack trace below.  

Stack Trace:

[HttpException (0x80004005): The current identity (NT AUTHORITY\NETWORK
SERVICE) does not have write access to
'C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\Temporary ASP.NET Files'.]
  System.Web.HttpRuntime.SetUpCodegenDirectory(CompilationSection
compilationSection) +742
  System.Web.HttpRuntime.HostingInit(HostingEnvironmentFlags hostingFlags)
+225

[HttpException (0x80004005): The current identity (NT AUTHORITY\NETWORK
SERVICE) does not have write access to
'C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\Temporary ASP.NET Files'.]
  System.Web.HttpRuntime.FirstRequestInit(HttpContext context) +936
  System.Web.HttpRuntime.EnsureFirstRequestInit(HttpContext context) +90
  System.Web.HttpRuntime.ProcessRequestInternal(HttpWorkerRequest wr) +270