Thank you for your message.
No, there is no limitation as to Windows XP support, any service pack. Regarding the Internet speed - although the more the better, there are still no specific limits because remote connection should work fast even on slower Internet speeds.
As an improvement, it would be nice to have a button at the bottom of the Agent to 'Disconnect + Close', because if you try to close on the Agent's window cross this one gets close but Viewer receive a message about retrying connection.
You can close the Agent using the regular Close button at the top right corner.
On the other hand, if you close the connection on Viewer's connection cross, the connection is closed but Agent don't close.
The Agent doesn't necessarily have to close if you close the connection on the Viewer side.