So long as its a legitmate copy and you have the information code showing proof of purchase it shouldn't be a problem.
Funny... NOT! It wasn't sat upon, but rather the pressure from the center holding peg in the case being too tight caused the crack.
I learned this little idea awhile ago - whenever you get a program that you install off a disk, do a full copy of the program files to your hard drive or external hard drive. Then you just simply click the exe file and off you go in a case like this.