Please do not take what I said in the wrong way, it's just that we can't guess what you are trying to do if you do not tell us exactly what you want. It's like if someone comes here and post a thread saying "help my computer isn't working". How isn't it working? What are the errors? We cannot guess them, nor throw solutions blindly. When you ask a question or assistance on BleepingComputer, and on any other forums for that matters, you have to be as clear as possible otherwise you'll get thrown replies, answers, solutions, etc. that doesn't apply to you, or that you aren't looking for. Since you knew that you wanted a program to clean Firefox's cache, you could have stated that at the beginning, and I would have insisted on using CCleaner right away, without mentionning the Windows Disk Clean-up Utility.
Also, I don't know if you realized, but two users so far (John and I) were concerned with helping you and offered you suggestions