OS is full?

Hi

I'm having some trouble with my computer, my father got it fixed last summer and the guy had to give us a new hard drive, but we still have our old one in drive (E). Although, now I'm having problems with my new one. Is says the (C) drive is almost full. I tried cleaning the disks and getting rid of old files but it hasn't done much. It currently says I have 920 MB free of 59.6 GB. While my old hard drive has plenty of space. Any suggestions?
Thanks

Welcome
Lets try several things first.
Download and run windirstat, to see what is taking up room
WinDirStat - Windows Directory Statistics
If that does not help, run a hard drive test to make sure the drive is not failing.
Hard drive scan usings SeaTools - SeaToolsfor Windows | Seagate - Both long and shorttests
This article should, also, be useful
How to Fix Shrinking Disk Space in Vista « My Digital Life
Run a full antivirus scan
Download and run a free scan with malwarebytes.