I say prepare for the worst. Do you have an external hard drive? That is the easiest way to backup a computer, which, even through my laptop runs amazingly, I should probably do as well. :P

Of course, you SHOULD back up your files every month or so, and save any important files to not only your computer but a handy flash drive as well.

In fact, I keep my 8 gig flash drive on my cell as a cellphone charm along with the tanuki. :)
It's always great to be able to access your data! :D

If the computer it self is making a viabrating noise that might be a sign of a loose part of something in one of the fans. Maybe.

my chatting computer was doing that for a while... then the fan on my graphics card failed.

that was about 2 years ago.. and i still havent replaced the card or the fan... i just dont run any high-end graphics on that computer anymore. :P

thats what my gaming rig is for.

Yeah, depending on where the sound is coming from, its likely a ball bearing in one of the fans. I had mine do that for about a year before I had to replace the graphics card. But backing up is always a good idea.