Optimizing a PC entails making certain changes to the system settings and software that can allow the computer to run faster and more efficiently. This can involve reducing the amount of data stored on the drive, disabling unneeded background processes, and other performance tweaks. Cleaning up a PC involves removing unnecessary files and programs from the machine and defragmenting the hard drive to ensure that everything is stored in the most efficient manner. Cleaning up a PC can help to improve its speed and responsiveness but does not necessarily optimize it for maximum performance.