Why wouldn’t my computer start?

Q: Why wouldn’t my computer start? Power light was on, fan running, but would not start up. I recently installed Firefox 11, and have about 10 add-ons from their site. Right before this problem, I was searching for a how to site and in the suggestions list was a link for Ron Hazleton online. Right after I clicked the link, my computer acted funny and everything stopped responding. After a few hours of powering up and down and hitting ctrl+alt delete and doing windows memory diagnostic, Finally, Startup Repair attempted to repair whatever problem I was having. When it was done, it said it could not repair the problem automatically. I was given a choice to restart, and so I did. So here I am. What the ** happened?