'88 528e broken cable and flapping/knocking noise?

Two days ago I was driving home from work and I noticed a flapping noise whenever I accelerated. The speed would change with the engine speed (the faster I went the noise sped up) and it got gradually worse, now the noise is there even when the car isn't moving. When I looked under the hood I noticed a broken cable right on top, I don't know what it is or what it does. I thought it might have been a belt but those seem fine.

Here's a picture of the cable:
http://www.shutuprobot.com/brokencablething.jpg


I also took a video of the engine and you can hear the flapping/knocking noise clearly here (5.7 MB AVI)
http://www.shutuprobot.com/badsound.AVI


So I'm trying to figure out if I should take it to the mechanic (probably yes) OR if it's something I could fix on my own OR if my roommate is right in saying "If it still runs, it's safe to drive!"

Any help would be greatly appreciated, thanks guys! :D