I found a really excellent tool set for removing stripped screw and nut heads. Made by Irwin - makers of Vise Grip. I have 2 sets, one is for rounded off bolts and the other is for rounded out/bunged up screws or broken off studs. It's like an Easy-Out extractor, but the reverse thread part is female. Fits over the head (or broken off stud). No drilling required. About $20 a set, but worth it.
I got the first set from O'Reilly autoparts. There were coupons for a free set of the other variety hanging with them.
This purchase was spurred by me stripping out some of the silly-putty like phillips screws on my Suzuki on/off road M.C.
I put the correct size extractor (trial and error) over the head of the bunged up screw, it digs in as you turn it, and SNICK, off it comes.
Just found the website -
http://www.irwin.com/irwin/consumer/...rwinProd410002 - The one that should work for you.
And
http://www.irwin.com/irwin/consumer/...rwinProd100314 - The set I got for free.