Hello everyone. Excuse my ignorance, but is C drive supposed to lose its free space drastically even if you don't add anything in there? I'm using a laptop and when I clean re-installed my OS (Win 7 64-bit) in early October, I partitioned the hard disk into three drives (C/D/E), and allocated about 50GB to C drive. When I finished installing everything I needed, I remember I had at least 8GB left in C drive. Recently, I noticed it was reduced to around 5GB, and during the last several days it was reduced to about 3GB.....2GB.....and now, I have only about 1.5GB left.
 
I use C drive for only applications and VSTs (.dll files), D drive for library contents (except for those I can't choose to install in there, such as Studio Instruments), and E drive for everything I create and save, such as projects, presets, documents, pictures and videos, and my download path is also E drive, so I don't think I'm adding anything to C drive. I've run Disk Cleanup and Disk Defragmenter but they didn't help much.
 
I think I have two questions here.
 
1. I've checked the sizes of folders and one file that are directly in C drive, but the total size of them (32,308,194,774 bytes) doesn't match the size of C drive's used space, which says 50,685,140,992 bytes (or 47.2GB). Why are they so different? I have the "Show hidden files, folders, or drives" enabled (I can see ProgramData folder).
 
2. Is there any data (which I didn't create) I no longer need and can delete from C drive? (other than those I can delete by Disk Cleanup)
 
Any information or suggestions would be highly appreciated. I don't want to see no space left next week. 
 
Thanks

Have a check for your Temp folder in User/App Data/Local/Temp
 
That can swell quite a bit. Also is your recycle bin emptied?

Amongst other things, that could be your swap file increasing in size, swallowing up your drive space.
 
You can tell Windows to use a different drive for the swap file.
 
Have you been downloading anything from t'internet?  That usually goes into the Downloads folder on the system (C) drive, you could move that data onto a different drive.
 
Also, if you install things, they often unpack to a temporary folder on the system drive and don't always clean up properly after themselves, that can add GBs of data you can clean up (check all possible temporary file locations and clean them of files).
 
Is there anything there you could uninstall from the system drive and install on another drive?
 
Could you backup stuff under My Documents\ (or even c:\users\your_name) to another partition?  Music, pictures, videos etc.
 
I would say that 50GB is just not enough these days for a system drive.  My system drive (a physical disk) is 280GB or so and I'm constantly fighting against it filling up, it's a battle that I will probably lose at some point.  MY 1TB drive also completely filled recently so I needed to stick another TB drive in and move a huge chunk of data onto it (I was q. surprised to fill up an entire TB disk!!)
 
[edit]
Some temporary file locations to check:
 
C:\Users\your_name\AppData\Local\Temp <- this folder on my work machine has half a GB of crap in it!
C:\Users\your_name\AppData\Local\Microsoft\Windows\Temporary Internet Files <- 3/4 of a GB!

There is no gain by partitioning your drive in this way. In fact some would say that you've created more problems by doing this.

We always recommend 3 HDD but not 3 partitions.

Files invariably take up more space on disc than the actual file size. This Is due to the size of the blocks into which each HDD is divided. 2 different files can't use space in the same block so there is always some space left over in each block. When files are written to disc.

are you running Win7 SP1? There was a fix in SP1 that fixed the fact that there was "missing" space when you compared free space in windows to what was actually on disk,
 
 

If you open Windows Explorer and navigate to your C: drive, you will see up in the right corner of the window a little search box.
 
Click once on that search box, and it will display a new menu tab up at the top of the window, just to the left of center, called Search, with some options.  The options include things like: Kind, Size, Other Properties, and you will also see just to the left of those options, a calendar icon with the words Date Modified underneath - with a drop-down arrow.
 
Click on the drop-down arrow (or on the calendar icon) and a list of choices will be displayed.  Since you are looking for recently created files, I would suggest you pick perhaps 'This Month', and it will search your C: drive for any files created this month, displaying the results for you to review.  
 
If you need to go back farther, try searching again, for 'Last Month'.  If that doesn't give you adequate results, you can select a range.  To select a range, rather than clicking on those options from the drop-down, click again on that search box and this time replace anything already typed in that box with:
 
datemodified:
 
This will cause a different thing to display - which will be right there at the search box.  It will display a calendar with dates on it, and you can just drag across dates to create a range.  It will automatically search after you release the mouse button after completing your date-range mouse drag.
 
(You could have also picked on the This Month or Last Month options from this set of options, but I gave the first technique so you could avoid having to type in datemodified)
 
 
That should give you an idea of what's filling up the drive.
 
Bob Bone
 

It's probably populated with your restore files, decrease the percentage used for restore files...

Google WINSXS. Win7 started out life using about 11GB on my system drive; three (?) years later it's more than double that, and WINSXS is now larger by itself than all of Windows was to begin with. 

some may shoot me for this...but go to "filehippo.com" and download "CCleaner" and run it.  It will show you a large amount of stuff that can be eliminated, and you'll have the option to keep what files you want as well.

Actually it's the shadow copies. Do this:
 
Click on Computer
Right click on your C drive select Properties
Click on the Disk Cleanup button
When the next box appears, check everything listed
Click on the More Options tab
In the box for System Restore and Shadow Copies click the Clean Up button. It will bark at you but do it a anyway.
Click Delete on the pop-up box then click OK on the Disc Clean up Window.
Click Delete again and walk away for a bit as it may take a minute or more.
 
This will get rid of a lot of junk files left behind by Windows. I do this monthly and get about 4 gig back, on my sister' machine I did this after a year and got close to 40 gig back.