While its for linux, this is a good examplethis is a good example of a question where the answer involves original code. Its a small program but the source code is available on a reliable host. The use of the software is clearly explained, as are the prerequisites for building it.
I'd think there's several criteria here.
Is the chosen host one that avoids linkrot - putting files on github or sourceforge is better than shoving it on $randomfilelocker, as many megaupload users have found out
Can the file be verified as being reliable? For example if you're linking DLLs from $random dll site, it may not be a good thing. If you can link a repair tool from MS, on the other hand, it would be better.
Do you have permission to share the file, and does it comply with the current rules at SU and SE, explicit or otherwise? For example, we don't allow hackintosh questions - linking something like boot132, which is pretty much only for setting up hackintoshes would be bad, as would say, putting up an upload of some non trial, proprietary software.
Do you provide a good, understandable writeup of what the file is for, and how it needs to be used?