Hi 
During ColdFusion 10 install, you might have Choosen ALL option during Configure Webserver. Which means, that ColdFusion handlers like .cfm, .cfc etc are added to the IIS (server level)
Every website under IIS say there are 10 websites under IIS, then all these will be able to serve ColdFusion ( say .cfm) pages. In future, even if you add new sites, you need not to create connector using Web Server Configuration tool as well.
To confirm handlers on server level in IIS 7, highlight server name (just above Application Pool in left panel) and then click on Handler mappings. If you are able to see ColdFusion handlers (.cfc, .cfm) just double click on any one of them and check the Exectuable path : C:\ColdFusion10\config\wsconfig\1\isapi_redirect.dll
Folder number 1 in the above location shows that you have 1 connector configured with All websites. If you create individual connector for each site then there will be more folders like 1, 2, 3 and so on and when you check the handler mapping for individual site, handler of each site will show the executable path for it's own connector folder.
Regarding the 404 error, frankly speaking you are the best person to resolve it in the entire world 
As it is a straight forward error.
Regarding 500 error, this is a generic error provided by server which can maen anything.
In order to troubleshoot 500 error, first step you can follow is to check Application pool. If you have installed ColdFusion 10 64 bit and configured the website as 64 bit (connector using Web Server Configuration tool) and the application pool of your website/sites is 32 bit then you will get 500 error.
So, click on Application pool in IIS, highlight the application pool of your website/sites (will be of the same name as of the site if you did not change it) and right click > Advanced Settings. If enable 32 bit is set to true that means your website is 32 bit. If you have configured connector with this website or with All then either you can configure the connector as 32 bit or set Enable 32 bit as false.
Hope it helps
Thanks
VJ