…or do I have to have a full-version CD?

I want a free registry cleaner that does what it is supposed to do.

my computer is almost a year old old and now its starting to slow down especially the internet how can i clean up the hard drive without deleting files and folders..i dont really have any programs i dont need so i dont know what to do help please i hate wen computers start to slow down i dont have paticnece with them

i have a windows xp, and when i try to play a video, it freezes the computer. also the computer for some reason is kinda slow when a page is trying to load. what can i download or do to fix this for free?
also i tried using CCleaner, and the computer still freezes when i try to play a video. i dont know much about computers so im not sure exactly what to do to fix these things