Where all my SSD space goes?

Wait, you said you only had windows 7 and GW2 installed? that took up 82GB of space?

If that is really the only 2 things you have installed (windows 8 and GW2) I would format your drive. Not like you are going to remove anything you cannot put back on.

Windows 8 64bit should take around 20GB I hear. GW2 (if i remember right) is about the same or less.

you should have 70GB+ free space. I say 70GB because the SSD is going to take space for its own files. It should not be too bad.

i bought it as 120GB, but the system only show 111GB useable.

I saw a folder name "Windows.old" that took up 20GB space. Base on what i understand, that folder keep all the things that i have in the previous Windows 7. Should i delete it?

Windows only needs about 20-25 gig roughly depending on your configuration. If your SSD is that full, it may be time to move some stuff to another drive, ya think? Understand that also if you did an inplace upgrade, all your old files and windows installation will saved under a file called something like "windows.old", and it can easily be 100 gig.

reformat the entire drive. that is going to be the best way to make sure you have a clean windows 8 install.

If you have only GW2 that will be the best route.

I think you need do the tweaks your SSD (for win7 or win8) like Disable Hibernation, Disable Prefetch and Superfetch, and Disable System Restore, etc. Check the link

http://www.computing.net/howtos/show/solid-state-drive-...

http://thessdreview.com/ssd-guides/optimization-guides/...

If you like have the win8 start button, you can download this Win8 start button for free
http://windows8startbutton.com/

+1 cin19

Remove the pagefile.sys. That file can be like 8 GB

Usually upgrading from one Windows version to another is not what I would recommend based on my personal experience. First, the system is never as fast and responsive afterwards compared to a clean install and merging the old registry to the new ones increases the chances to get weird bugs, etc... Also it kept a lot of files that it doesn't need from the previous Windows 7 so this is probably why you lost a lot of space.

As others already mentioned, my only advise would be to format the drive and reinstall Windows 8 with a clean installation. Also look at Cin19 advises to better optimize your OS for SSD and also save additional space. Another thing you could disable is the automatic defragmentation, I heard that SSDs don't need it and it would only reduce its lifetime.

Windows 7 and 8 should automatically disable the built-in defrag on SSDs.