It's worth noting that you need to empty the recycle bin after deleting things for them to be truly marked as free space. Additionally, a great tool to clean un-necessary files is CCleaner which you can get from www.piriform.com/ccleaner.
Check the space allocated to system restore and cut it back some. Running Ccleaner is a good idea too. When it asks to backup registry items before deleting select yes, You can manually elete them later when you are sure there are no problems.