I get this error message when trying to register. I have disabled almost everything within Comodo Firewall, and its still not letting me get anywhere with it.
Are you running any security software that prevents writes to the registry?
Ewen 
Hi,
Also checkout our knowledgebase article:
Garry
Got it. I installed the latest script version that windows had after noticing that I didn’t have the msxml3a dll file. And I also registered the msxml3.dll in the registry. Also I didn’t have any software that prevents writing to the registry.