So I just defragged my computer, rebooted, and when steam tried to boot itself up, it returned a popup message saying there was an error, and that to turn off compatibility settings for steam.exe to run.

So I went to my steam folder, and turned off compatibility mode for steam, and voila, no problem.

I wanted to find out [b]why[/b] this suddenly happened. I did some research using google, and I found forums and discussions regarding this issue.

One thing I noticed was that all the answers to the questions people were asking about this problem, involved editing the registry. Which I think is very unnecessary.

None of the discussions I found gave any answer as to [b]what causes[/b] this issue to happen. That's what I want to know, because if this is going to happen again, I'd rather fix the source of the problem to prevent this.