Dude ignore the other comment left it doesnt make sense and you will damage your pc

PC repair software only repairs registry files, internet cache files etc. It by NO means will adjust any physical properties such as your CPU speed etc.

Your PC is probably slow because there is so much software running in the back round which you dont even need and half of it is probably spyware.

go to startmenu/run/msconfig and click the boot tab and also have a look under the start up tab.

This is a list of all the programs that windows needs to start up. If you are unsure of exactly what the program abbreviations mean simply google it.
Its pretty easy, just untick all the crap that isnt being run by microsoft UNLESS you know exactly what it is.

Anything which is being runned by Microsoft should be ok to run.
After that defragment your hard drive (Startmenu/accessories/system tools/disk defragmen) (Make sure you clean all temp files, this tool is located in the same directory "disk clean up"

If this doenst help reformat your PC.
If your dead set on increasing your processor speed you need to go into the bios and over clock it BUT your motherboard might not support it and you run the risk of frying your cpu