As Tuvok says, if it doesn't work take it back.
With regard to missing memory, there might be a lot of temporary files (possibly created when installing the operating systems) that are taking up all of the space.
As an analogy, it took me a while to find out where I was losing all of my hard drive space on the Windows 7 PC (with just a 64Gb hard drive) that I'm using to type this. It turned out to be well over 20Gb of temporary Internet Explorer files that were causing the problem, even though I never use Internet Explorer! (I'd been streaming a lot of internet radio via Windows Media Player and had forgotten that WMP shares temporary folders with IE).
To find out where you're losing disk space on a Windows system, use WinDirStat:
https://windirstat.net/