Hello SNsCPU, can you confirm that you have trim enabled?
To enable TRIM, start a Command Prompt window (in Administrator mode, type “CMD” in the Search bar from the Windows Start Menu) and
enter the following command:
fsutil behavior set disabledeletenotify 0
How do I know if TRIM is working in Windows 7?[/size]
To check if trim is working open the Elevated command Prompt window, type the following:
fsutil behavior query disabledeletenotify
Results explained below:
DisableDeleteNotify = 1 (Windows TRIM commands are disabled)
DisableDeleteNotify = 0 (Windows TRIM commands are enabled)
When windows deletes files on a SSD they are marked for deletion but not actually deleted until trim does its job, this is not a problem for windows as it knows that the files have been marked for deletion. When another program looks at your SSD it may see the undeleted files and misreport the space and this is what I believe is happening here.
With trim enabled log off and leave the PC alone for approximately 2 hours the first time and thereafter one hour a week This will give the trim command time to work and free up the space on your SSD.
Even with trim working, because of the way it deletes blocks on the drive there will always be some unerased cells on the drive.
Have a look here for a more complete explanation;
How to Enable TRIM Support for Your SSD « Corsair® Blog