If you try to install it on a Windows Server 2008 R2 64Bit you might see 2 issues with that:
After installing you click "Start - SQLXML 3.0 - Configure IIS Support"
If you get the error
"An error occurred connecting to 'server'. This server does not exist or is unavailable."
apply the following solution
Click "Start - Administrative Tools - Server Manager"
in the Server Manager go to
"Roles - Webserver (IIS)"
Go to section "Role Services"
verify that all of "IIS 6 Management Compatibilty" packages are installed.After I installed the IIS 6 compatibility packages the SQLXML 3 snapin starts and connects just fine.
The second error can occur if you attempt to call one of the xml templates and IIS just gives a 500 error 0x800700c1. Permissions and all appear correct. The IIS Virtual Direcotry Manager for SQLXML 3.0 throws an error when I attempt to Restart Application DLL "Error occurred unloading the application".
Then apply the following solution:
1. Open IIS Manager, Select Application Pools.
2. Under Actions pane, Select 'Set Application Pool Defaults'.
3. Set 'Enable 32-bit Applications' to 'True'. (Solution found here)