hmmmm well I'm not sure but on old magnetic drives the data was never precise but that would not be the case of SSDs. Windows formatting usually takes away about 1 to 10 GB for backup and recovery partitioning, and 20 gb for formatting but still, that would only be 40 to 50GB used up. I would reformat and reinstall one more time.
Another thing you have to look at is the page file. More than likely, it set up a HUGE page file. You can easily change the size of this without having to to reinstall, so i would check it first.
start>right-click "my computer" and click properties>click advanced system settings>click settings under performance>go to advanced tab. Under advanced look at virtual memory and look what the size is.