Coldfusion 10 localhost not working

There is so much that could be amiss, and that you are not saying. This may be a tough one to solve only in the forums. But adding yo what Rahul said, a few questions come to mind:

• you say in the title "localhost not working", but the URL you show using is 127.0.0.1. They are not technically identical. Have you tried the admin URL with localhost instead?
• are you saying that you previously did access the CF admin with a URL like that (with either that IP address or localhost), and it worked? are you 100% positive? are you sure you didn't need to add a port, like :8500 before the first slash?
• Do you know what site in IIS is running your localhost requests? It is probably the default site. Is that site running? (I know you say you get a 404, which means file not found, but it's worth checking)
• And speaking of the 404, are you able to confirm that that site (the default site, I assume) has a CFIDE virtual directory in it? And it has an administrator folder in that?
• If it does, if you right-click on that administrator folder (on the left panel of IIS), there will be a "manage folder" option with a "browse" option. When you click that, IIS will open your browser to the URL that IT thinks should be used for the site in question. Does that work?
• Also, though you are making the request on the server itself (since it's a localhost one), I will point out that a 404 is what you get if someone configured the "error pages" for that site a certain way. I will not elaborate on that for now, as it's complicated to explain easily. But if you still get a 404 when visiting the URL that IIS opens (per the last step), then you probably have some other error causing the problem, and would need to tweak those "error pages" settings back to their default to get it to show you the error. I will hold off explaining that.
• Also, look at the "application pools" section of IIS. Are all the pools started? By default, each site gets an app pool of its own name. (Again, it's too complicated to help you confirm if that's the case for your setup.)
• Moving on, you say you added a new site and now "it's broken". What is? the new site? What URL are you using for that? what error do you get? a 404 or something else?
• And are you testing that new site from a browser on the server itself, or from off the server?
• Are you sure that the new site is started? and its app pool?
• Perhaps most important, abotu the "new site", does it have a jakarta virtual directory? (and does the default site)? It is vital in CF10 and above that a site have that jakarta virtual directory, pointing to an isapi_redirect.dll file implemented within CF.
• As Rahul notes, if you run the wsconfig tool, that WILL create that virtual directory. but to be clear, you don't HAVE to do that. You can just create that virtual directory manually (right-click on the site and "add virtual directory", calling it "jakarata", and pointing it to the same file that the jakarta vd in the default site (which should be there by default, since you say the localhost site used to work).

Hope you find answers somewhere in there, or it may lead to more quesitons. If you are in a hurry and need help today rather than waiting for people to see and reply here, there are consultants (like myself) who do this sort of troubleshooting, remotely, on a consulting basis. I even offer a satisfaction guarantee, so you won't pay for time you don't find valuable.

I list such consultants as a category of my cf411.com site (of tools and resources of interest to CFers), specifically at cf411.com/cftrouble.

Did you run web server configuration tool (wsconfig.exe) from C:\ColdFusion10\cfusion\runtime\bin ?

This would create a connector between IIS and ColdFusion.

-Rahul