Never, ever let your OS drive get that full. It absolutely ruins your system's performance. Keep a minimum of 15% free space at all times, especially with SSDs since being very full negatively impacts their lifespan.
I would suggest downloading CCLEANER which can be easily located at www.filehippo.com Check off most of the options except the last on in the middle list and the last one in the bottom list. Next right click your recycle bin and reduce the size to 400MB or 2% depending on your OS. Then go to your C:\ and right click it and turn off drive indexing and click on ignore all. After that is done if your drive had a lot to delete, run a defrag which helps a good amount only if it is bad.. If not to defraged it will not do much for you. Update your video drivers to the current ones, I suggest going to Nvidia's website if you have a Nvidia based graphics card.
As stated above you shouldn't let your OS drive get that full.It really slows down performance.
A good way to get some more space is to decrease the size of your paging file.You can do this(in Windows 7&Vista) by right clicking on My Computer.Then click on Advanced System Settings.Then click on the Advanced tab.Then click on the Change tab in the Virtual Memory section at the bottom.Select Custom Size and then change it to 512MB(that's what I have mine set at you can put it higher if you need/want to) for Initial and Maximum.