I did a clean install of Windows 7 on a new W520 with 160GB SSD and 32GB of Memory. After the clean install, I have only 74GB free space out of 148gb on my C:\ drive. (note: i didnt partition the harddrive)
Usually it is supposed to be 128GB free space out of 148GB after a clean install of Windows 7, so where did up to 50gb disappear to?
If you have more memory installed, Windows will allocate more free space for pagefile and hibernation. If it's around 50GB, most likely 18GB will be allocated for pagefile (if you have sufficient memory, the size of the pagefile will be slightly lower than the capacity of RAM) and 32GB will be allocated for hibernation.
To get back 50GB of free space:
1. Disable hibernation
Go to Start > All Programs > Accessories > Command Prompt, right-click, Run as Administrator > type: powercfg /h off and enter.
When it is successful, 32GB of space will be freed.
2. Disable pagefile
Go to Start, Computer, right-click, Properties, under the left side click Advanced system settings, under Performance click Settings.
Click Advanced tab, under Virtual Memory, click Change, uncheck Automatically manage paging file size for all drives, click on the drive with allocated paging file size, No paging file, Set, OK.
Restart your computer after apply this settings and you will get back your remaining 18GB of free space.