ATF Cleaner from http://www.atribune.org and CCleaner form http://www.piriform.com will each find and delete different types of clutter. If you open up to see hidden files and folders, you can delete all the files statring with a $ symbol in C:\windows, then everything in the Download and Event Cache folders within your c:\windows\software distribution folder.
That's about as simple as it gets but your thread title is confusing. If you're seeing a CD or DVD with no free space, that's because there's no space on the disk - not the drive. Your storage is in the hard disk and that's where you can make some room. If you go to My Computer and right click C:\ and go to Properties, you'll see a pie-chart showing the free space.[/#000ff]