Hard drive clutter

[Pavway]

I recently started removing programs that I installed that I are old or I don't use anymore from my C drive because I had little room left. After doing this and defraging I have a large space thats made up of fragmented files. How do I know if they are needed and how do I remove them. Is there a program that can tell whats needed and delete them? Also what about all the windows updates that are still there, once they are installed can they also be deleted?
Thanks - Paul