I've been working on pc's since the mid 80's (MS-DOS 2.x) and have seen a lot of changes and tried out a lot of different utilities for fixing computers.
Back at that time the go to program was Norton Utilities for working on DOS machines.
Today...there are tons of programs that say they will perform miracles. Let me say this. Any of the programs that tell you they will speed up your pc on tv are usually trash. Frankly, some of the commercial fix it programs are viruses and Trojans themselves (in my opinion)
I have found one I highly recommend to run periodically to clean up your registry and general house cleaning.
In other words, I trust, like it and recommend it.
System Mechanic by IOLO.
It's a fair price and they let you install it on all your computers in your home. It has real time features that work quite well.
It's not an anti-virus or anti-spyware utility. It just sits in the background and helps Windows keep from getting corrupted. I've seen it take computers that were giving the "blue screen of death" and 100% revive them.
Like most utilities you want to install and run it when your computer is running ok, not wait until there are problems.
About once a week or once a month, run it and let it clean up your registry at least. Disk defragmentation is one thing I always hear people talk about as if it will fix your computer. Not really. PC's are well adapted to working with fragmented files. It doesn't hurt to defrag maybe once or twice a year. Not that critical.
Keep your registry cleaned up.
Now...all computerheads have their own opinions. I promise you there are techs who will disagree with me.
My analogy about computers is cars. Put a Ford guy and a Chevy guy in a room together and ask them why their cars are the best.
Computer guys are just as bad. You just have to figure out what works for you and go with it.
Lastly, backup often. Get an external hard-drive that plugs into a USB port and backup important files frequently. I use FreeFileSync.