I had Gratuitous Space Battles, but it got uninstalled when I rebooted my computer. I have no idea how to reinstall without re-buying it! Please help!
First of all, welcome to the forums.
Now, we will need a bit of information to be of assistance. First (and probably most useful), did you buy GSB direct or did you get it through a service like Steam?
I got directly from the website, not on steam.
In that case it sounds like you would have gone through BMT Micro.
For the quickest solution, try and find your confirmation email from BMT Micro and try the download link as it may still work. You will need to find it anyway as it will have your online code.
If you cant find it then send an email back to BMT Micro and provide enough information so they can backtrack your purchase and send you a new link.