I am useing Windows XP and wanted to know if  when I hit the right button and then hit the explore when the files come up. I go through each and every file to see if there is any files I can delete. Some file folders are writting in blue and some are written in black and I am not sure if I can delete them, Also wanted to know that the files I find that are titled cache, and temp folders if I can delete the contents of the folders. Any help would be much appreciated and thank you ahead of time.

Goto my comp --> Right click on your drive --> properties --> disk cleanup

Do this for all drives. This will only delete unused old files, compressed files, temp etc