[JAceves]

Whoever stated that games don't harm the computer is wrong (since everything you do harms it...)
Games CONSTANTLY use system resources, which some of you forget that it is actual physical hardware. It can be worn and overused.
Windows will harm the computer without your knowing because it doesn't run a filesystem check as a regular practice (this should be done, leaving files open in an os leaves lost data sectors on the hard disk). I believe windows did (pretty sure it still does) leaves a membrance of every library it uses till shutdown when it takes care of closing this cashe, but its hard to trust that because you can't moniter this process. Also an improper shutdown will also cause the above stated problem.
So yes, graal can harm your computer... but so can everything else. The program itsself doesn't change any internal settings, just adds registry keys which remain even if graal is removed.