I am not a fan of any program that automatically cleans the registry. One mistake in the registry can cause an operating system to be inoperable. I find they cause more problems as they try to repair them.
And just a couple more comments to add...
Defragging a hard drive with today's operating systems is really not needed IMHO. Back when the file system was FAT32 it helped but not so much with NTFS.
And having more than one virus scanning software running at the same time will cause the system to slow down. For example having Microsoft Security Essentials and Trend Micro both running. Only one virus scanning software should be installed and used. This is a very common mistake for a system running really slow. You have two programs competing with each other to do the same job.
And be aware what programs are running during start up and the background. Some programs like webcam software will run during startup and stay running in the background. Unless you are using the webcam then this is not necessary. At the right hand corner where the system clock is located there are little icons that indicate what programs are running. You can right click and close them. Also removing them from the Windows startup folder will keep them from restarting after rebooting the computer.
