Here is how to successfully migrate a SQL Server Reporting Server Instance (SSRS) from one location to another using the same major database release. SQL Server 2005 -&gt; 2005 for example. These steps also apply if you are looking to migrate reporting services to a dedicated report server or x64 instance of SQL Server 2005 or 2008.<!--more-->
<ol>
	<li>The number one step is to install Database Services and SQL Server Reporting Services on the target machine to be migrated to.  Making sure the service packs are all up to date on both instances is always a good step as well.  When asked, select to create a default SSRS instance.</li>
	<li>The next step is to Backup the ReportServer and ReportServerTempDB databases on the source machine.</li>
	<li>Back up the Report Server encryption key on the source machine.  To accomplish this start the Report Server Configuration Tool and navigate to the encryption keys section.  This will require you to enter a password for the key.  This password will be needed later when restoring the encryption key to the target server.</li>
	<li>On the target Server.  Restore both the ReportServer and ReportServerTempDB databases with the overwrite option to overwrite the default config machines created in step one.</li>
	<li>Open up Server Manager and navigate to the Services Console.  Change the service accounts for SQL Server and Reporting Services to the desired accounts matching them up with the source server.</li>
	<li>Open up the command prompt and type "RSKeyMgmt -l" to get a list of the stored encryption keys on the target server.</li>
	<li>Delete all of these keys with the command "RSKeyMgmt -r &lt;keyid&gt;".  Repeat this command for all the key ids listed.</li>
	<li>Go to SQL Report Server Configuration tool on the target server and configure all services and tabs to mimick the credentials and settings of the source server.</li>
	<li>On the Encryption keys tab, import the encryption key backed up from that source server using the password you specified.</li>
	<li>Navigate to C:Program FilesMicrosoft SQL ServerMSSQL.xReporting ServicesReport Serverrsreportserver.cfg and edit that xml file.  Delete the encrypted values in the "username","pwd" and "domain" sections.  Replace this with the appropriate domain credentials and save the config file.</li>
	<li>Restart IIS and navigate to the new servers report address.  <a href="http://targetserver/reports">http://targetserver/reports</a></li>
</ol>
Below is a good MSFT Knowledgebase article on how to do this as well although there are some omissions.

<a href="http://support.microsoft.com/kb/842425" target="_blank">http://support.microsoft.com/kb/842425</a>