I've been doing PC repair and IT administration for almost 10 years now, and here are some things that I hope will help anyone fixing PC problems. If you follow these tips you should be able to resolve 90% of your pc problems.
1. This is the most important tip that I can give anyone at any level of expertise. KEEP IT SIMPLE. Most issues have very simple solutions, if you over complicate it the answer will be hard to find.
2. Check the connections, is everything plugged in? This question irritates even me when tech support asks it but the fact is TRY THE SIMPLE STUFF FIRST. Make sure all the cables are plugged in properly and are secure. Additionally are all of your expansion cards tight, are all the internal cables plugged in properly. Numerous times I have had to take the side cover off of a brand new machine to plug in an IDE cable or a power cable.
3. What has changed? What is different now that you are having problems. Have you installed any hardware or software? Have you applied any security patches, or updates? Has anything changed in the physical environment?
4. Try a reboot Sometimes, as silly as it sounds, this can fix many problems. Unplug your peripheral devices shut down the PC for several minutes and boot it back up again. It is always worth a try.
5. Viruses and spyware. What can I say these days malware accounts for about 75% of the problems that I deal with. Make sure your anti virus definition files are up to date and do full through system scans. Don't be afraid to use on-line scanners or stand alone tools like stinger.
6. Hit the blogosphere. Chances are someone out their has already faced your problem. Don't be afraid to ask for help. There is a wealth of knowledge out there and don't be afraid to share what you know with others.
7. Don't spend too much time on your problem. It doesn't pay to get frustrated, walk away. Sleep on it. Sometimes a fresh outlook is all it takes to uncover the answer.
8. Determine if the problem is hardware or software. If you can answer this question I'll bet you can solve the problem much more quickly.
9. Replace suspected bad with known good. OK OK ... I know everyone out there probably doesn't have a whole pile of parts to test and troubleshoot with but most of us have more access to spare parts than they realize. Give it a try.
10. Don't put a lot of faith in those software packages that promise to identify and solve your problems for you. My experience is that NONE of them are very good. Most good IT techs don't use them and there is a reason for that.