I'm running the game on a Virtualbox Win XP machine; my main system is Ubuntu 14.10. The game works fine, but it's completely unplayable because the mouse is so fast - if I move it a distance that would normally cover maybe 20 px, it's already taken up more than the whole game window.

I've googled but haven't found anything. If you guys have any suggestions, I would be very grateful.

It's a well known VirtualBox bug in games. The same one existed in Wine, but was fixed there years ago...

Just try using DosBox, if you mean the original one, or Wine, if you mean the 10 years edition.