Step by step way to remove old files that cause my computer to run slow.?

Using add and remove from the control panel similar in windows vista /windows 7 or 8 scroll through them to remove programs not being used , another way is using ccleaner to clean junk files and the registry option to remove old registry files , i use a program call fix-it utilities click /one click solutions / click clean up and it will remove all junk files to the recycle bin to be remove from the system another way is using windows disk clean up sometimes it takes a while depends on what older files needs to be remove , the program i use cost a small price and i brought it at walmart , try ccleaner and windows disk clean up first before getting into other clean up disk programs online

Plenty of free space. Your machine might be plug up with spyware or adware, or even have a virus. If you do not have a spyware / adware scanner, I would recommend getting one. Microsoft has a beta version of one, or use something like spybot search and destroy, spywareblaster, or adaware. It would also help to do a disk clean up and defragment.