Computer repair training plus develops a knowledge base and the appropriate 
skills needed to repair and maintain computers. There are many vocational, trade tech, and college level classes available. The Regional Occupational Centers (ROPs) where I teach are great places to learn. They are usually free or very low cost and provide working industry experts that give you valuable hands-on experience. I have had several IT college graduates that told me that this was the first time they ever got to actually touch the insides of a computer and apply what they learned. Application of the knowledge is what helps develop necessary computer repair skills. We take the computers down to the bare metal and then build them back up. You learn how to properly configure hard drives so that maintenance and backups are easy to perform. You will learn all about the Windows operating system and all its short comings and problem areas, such as, why is my computer so slow. You will learn about many open source utilities and programs that will help greatly in troubleshooting and maintenance. All this should be helping you to obtain the A+ certification from CompTIA . A+ will open many doors to this exciting field. There is some study you will have to do, but you will find it very rewarding as all the mystery of computers is revealed and you become a proficient tech.
The Computer Repair Training website has some additional information you might find helpful.