And you didn't back up the ISO file?

There's a pretty easy way to get a legitimate Windows 8 install image from Microsoft, if you need one:
http://www.ghacks.net/2012/11/10/how...windows-8-iso/
(unfortunately, no such way that I'm aware of for Win 8.1, and while 8.1 is a free upgrade once you have 8, they don't make it easy to install directly from an 8.1 disk with an 8.0 key. There is a way to do it, and it's kind of lose-lose being (A) doing it directly is a pain, and (B) the 8.1 upgrade is really, really slow.)

BTW my reference to the telephone support was to reuse the activation key if there is a problem with that.

Not sure who your university uses for their mall, although if you have the install key, you can always get the installer from anywhere (often including a legitimate copy without key Microsoft itself), and just reinstall using your key.

Which doesn't mean it isn't a good idea to back up installers as well as your keys.