If you are a Windows user I wanted to mention a utility that has served me well over the last 18 months or so. PCTools Registry Mechanic scans the notorious Windows registry, finds, and fixes problems automatically and accurately. Problems with the Windows registry account for many of the unexplained problems seen on Windows machines like spontaneous reboots, software that has stopped working, or just a slow plodding machine which was once much nicer. Anyhow the demo is free. If you want to purchase a license to use the software it is good for as many machines as you might have. BTW: I'm not affiliated with these people in any way, just a satisfied user. Highly recommended
http://www.pctools.com/registry-mechanic/?ref=google_rm&gclid=COiwo6vO5o8CFRJgWAodxinaDQ