C:\ might not be a problem, but we can't verify that without code. The path looks a lot like what I'd expect to see on an IIS server. On the other hand, it may be simply misconfigured in your file, but that isn't something we can tell you.
Assuming the path is correct, it looks to me that you'll be up the creek. As mentioned the 404 is a missing page, so it didn't upload successfully. If you don't have the files, than you'll be rewriting or downloading them again. You can try contacting your host to see if they have a backup available for which to perform a filesystem restore as well. If you're using a database for your data, than your data should still be intact and not require any type of restoration.
And now you've also learned why backups are *very* important. I manage an entire corporation's backup systems, and whilst people scoff and the importance of that role, the sure come crawling back when something needs to be recovered (ie: many times daily).
header('HTTP/1.1 420 Enhance Your Calm');