My aheadset had a little play so I needed to adjust the stem load unfortunately when I went to remove one of the two old M5 screws holding the stem to the steerer tube one of them was in such bad condition that the allen wrench spun inside the socket, stripping the head, ah crap!

BTW, the stem's two screw holes go all the way thought.

Let the adventure begin.

1. Bought a screw extractor at a Hardware store by my place (~$3) Used one of my regular metal drill bits to create a pilot hole to insert the screw extractor. The extractor went in fine but as soon as I applied pressure (twist to extract) it snapped flush at the edge of the hole.
2. A trip to Lowes to get two supper duper strong drill bits (two different diameter/sizes just in case, ~$7 for both) made out of cobalt. Also got a supposedly better bolt extractor ("Grabit" #2, ~$8) The drill bits took care of removing the broken piece of the old extractor and also made so much easier to drill a little deeper hole in the screw for the new extractor. The new extractor has a drill bit on one end that does not look very impressive and the actual extractor on the other end and is supposed to be used with a reversible/variable speed drill which I did. The extractor did not grab at all, its metal is way too soft and the thread to fine to work on the screw. No go.
3. Second trip to Lowes. Once returned the Grabit extractor (~$8 credit), I got a set of two Torx T30s (~$4). A torx T30 thing fits a 5mm allen head so in theory I could use it to unscrew my problem bolt. Got home gave it a shot; the T30 spun and made the head of the allen screw yet a little bigger :-|
4. A new trip to yet another hardware store by my place, this time looking for some serious epoxy. Got some JB Weld (~$9), to "glue" the T30 inside the allen head holding it in place with masking tape while it dry. While I was at it I used the leftover mixture of JB Weld to fix the cage of a broken front derraileur.
5. 24 hrs later removed the tape and used wise grips to try unscrew the thing. after just a little pressure the Torx got separated from the allen head. No go for the JB Weld. The Derraileur cage fix also was also a failure, granted I used just a tiny amount of JB Weld on it.
6. Running out of options here, time for a dramatic solution. Use a Dremel with a reinforced cutting disc to cut the screw at its exposed section (the adjustment slit on the stem) I did not wanted to do this before as if I slipped a little I could damage the finish of the stem (look who is talking) Anyhow slipped the Dremel in the stem slit, then slowly turned the power and worked my way until the screw was cut. Removed the half of the screw that had the screw head by using the Torx T30 and my fingers barely any force was needed, pretty easy. To remove the other half of the screw (the butt) I inserted a small 3mm allen wrench from the end of the hole opposed to the cut, and applied a little pressure while turning clockwise, yes clockwise. What do you know it turned... just a few turns. So now what? I screwed in a brand new screw from the same side and just turned clockwise and the screw butt came out the other end without any force.

New stainless screws went in (~$1) After about ~$24 and a couple of hours at home (plus the trips to the hardware stores) everything is good again and the load on the headset is adjusted, me happy, bike ready for another mixed terrain adventure. Oh wait, I should also replace the old rusted, cheapo, stem face plate screws before it is too late.

7. New trip to my hardware store for a couple of M5 15mm stainless screws (~$1). Lets say ~$25 of fun.