Help! Windows 8 eating away my C Drive


I have googled for days without really finding a good answer to why this is happening.

I always keep a small C Drive to be efficient. Its 35gb. But for windows 8 i decided to increase it to 50gb so i can install apps as they go in the C Drive automatically and you cant decide where they install.

So after installing fresh Windows 8 in november i had free space of around 30gb after drivers and other small softwares i think. I am not really sure but it was above 25gb. I always install Photoshop in Drive C. So after installing that and a couple of metro apps my free space was always around 20gb or more.

Within a couple of months that space has gone down to 15gb then 10gb. Then 5gb. And now its 1gb and everyweek i have to delete temp files else the free space goes down to 100mb!!!

I dont have any malware or adware. I dont have anything installed other than that i have mentioned. I noticed how windows doesnt delete old versions of metro app after updates. But that can not be the main problem as they are not big enough to take up so much space. I have disables hibernation due to this to free up a GB of space. But that too got eaten.

I then tried different softwares to clean temp files and corrupted update files and was successful in freeing up around 2 3GB... but that too got eaten!

I am back to 500mb of free space. And the biggest files in drive C are the Swapfile.sys. ad the Installer file and another file in WinSxS\ManifestCache.. and these are around 300mb each... So it seems there are smaller files that windows is not deleting or something. This never happened on Windows 7. And my harddrive is perfectly healthy.

Anyone facing a similar problem? Looks like i have to install a fresh copy of windows 8. :(

Any help will be appreciated.

UPDATE: I have run every utility. CCleaner. Disk Cleaner. Deleted logs scratch disks everything. Nothing solves the space issue. I ran WinDirStat. And here is a screenshot. This Yellow Unknown thing is taking ALL THE SPACE> anybody know what it is?