Server Files

I have a server running Server 2003. I partitioned the drives so C was allocated 20GB and D was allocated the rest. I have now come to the point where I am running low on space on C and I have critical updates that I need to D/L and install. I would like to know if there are any files besides temp folders that I can get rid of without causing any damage to the server such as log files. I know I could use a partition tool to give myself more space on C but I would rather not. Any suggestions?