we have just upgraded our server to a 64 bit version and I transfered all my websites over and every web site I access I get the following error message:

'

401 - Unauthorized: Access is denied due to invalid credentials.

You do not have permission to view this directory or page using the credentials that you supplied. 

any ideas?  Thanks

 Obviously you haven't got the correct permissions set.  Less obviously, you asked in a forum that is aimed at helping web hosts work with ASP.NET.  Since you're not a host and this isn't ASP.NET, you'll want to ask at www.iis.net, same login as here.

Jeff

By the way, make sure you understand what account IIS 7.5 on Server 2008 R2 is running under. 

Jeff