Dear Elete12,
First off what OS are you running? Secondly, what other programs are you running in the background while playing the game? I know of some reasons to memory loss. So depending on your software and hardware being used it might cause conflicts with memory usage. I see how you said you went and deleted a game and gained memory. So are you speaking about RAM "Random Access Memory" this is what gives your computer the ability to open multiple games and internet browsers and keep them open without slowing your computer down. But, the way you worded your message it seems like your having storage memory issues. If this is correct you need to run a system diagnostic and see if there might be something to be found there.
So just a little about how memory is used while playing games or using a program.
Basically, when a program needs to use something, it'll put it in your memory. When it doesn't need it anymore, it'll send the signal to get rid of it since it's no longer using that particular piece of information. A memory leak happens when there's a bug in the code that forgets to send that signal, so every time it needs that piece of info, it'll keep calling it back up, but the old pieces will never leave, so it will continue to use tons of memory (RAM) over time to the point of making whatever game or application you're using unusable.