If you have two hard disks it might be trying to use a temporary folder on the smaller disk.
Folders as such don't have a size limit but some programs create lots of temporary folders which can soon take up a lot of disk space (and don't always remove them when finished, especially if a problem occurs).
Have you tried running the free program CCleaner? Got rid of an amazing pile of temporary guff on my drive from places I never even knew existed. (
CCleaner - Optimization and Cleaning - Free Download)
Another possible (but unlikely) reason for lack of space is programs reserving memory for their use and not releasing it. Windows gets all in a bother about it at times and loses the place. When doing something using a lot of space or memory I usually reboot to clear the memory and run the space-hogging program on its own.