I downloaded Autodesk Revit 2013 when I trying to install there is a message: out of disk space. In that case my hardisk on Part C still more space (19 GB,). System requirement was 5Gb free disc space require. I can´t install Revit now.
You need lots of space for the installation temp files and downloading of the materials library. Probably should have about 40GB free for installation.
I think this article can give you an explaination why you out of disk space:http://upandready.typepad.com/up_and_ready/2012/06
So I would suggest you to move your download and extracted files to D disk, and empty the temp folder, then try to install.
If my post answers your question, please click the "Accept as Solution" button. This helps everyone find answers more quickly!