Broken bolt for drive pulley, advice needed.

I have sheared off the head of one of the three bolts that attach the drive pulley thing (I forgot its name). My question is, should I try to have it tapped out, or should I go through the process of removing the entire pulley to get at the bolt? How would I go about removing the pulley? Also, I have included a picture of another mysterious bolt I found resting next to my belt, but I cant seem to find where it came from. Any ideas?
More pics here: http://imgur.com/a/5X1Nz

http://i.imgur.com/ypUU3Bg.jpg

Ez Out...unless there's enough sticking out if you take that pulley all the way off and can get some vice grips or such on it.

+1

I did the same thing once. Just pull the pulley. Much easier to work on. The hole is a through-hole too so, if you need to, you can work on it from the back. I tried an EZ out, promptly broke it off. Aauuugggh! I then drilled from the back and got it out. Major PITA but I made it from "broken bolt" to "fixed" in about four hours, including the trip to Lowe's for the EZ out and the replacement bolt. Good luck.

I think there is enough to get some vice grips on it if I take the pulley off, so that is what I will do! Thanks guys!

I read an article about the effectiveness of penetrating oils, the most effective was a 50-50 mix of acetone and brake fluid. I have not tried it yet, but I have bought some acetone. I have been using PB Blaster and like it. Be sure to use some penetrating oil before you grab the bolt with your vise grips.