Here is an easy to use concoction of software that does a good job of speeding up a computer (assuming it's not slow because of viruses).
First uninstall unwanted programs using
Make sure you choose the "Advanced" Option when uninstalling a program. It will uninstall the program as usual, then go back and delete all registry entries and leftover files.
Then, download and run it. Also, choose the registry cleaner tool once it's done and run it too. The only option I would uncheck is the "Unused File Extensions"
Last, download and run . Go in the program options beforehand and choose to put the system files at the beginning of the disk.
Run Ccleaner and Auslogics Disk Defrag once a month and your computer should be humming along nicely.