kkhigh....you leave the can intact and on it's side, make sure you cover fully with at least 1/2" of water....I covered with more than that. I put the lid on the pot and let it boil on just about high for 4 hours. I would check carefully every so often that the water level was still above the can and just kept adding more hot water when needed.
It is important to keep water level up over the can to stop it from exploding apparently.
If you go through the first part of this thread it tells you all the how to's.

thanks for the info...i have read this thread several times but you answered my question about leaving the lid on the pot. Thanks! i just wasnt sure about that part because i had never boiled anything with a lid left on before. (only use the lid to help bring something to a boil then removed it)
anyway, thanks again!
-kim

well, that little squirrel is all over the place isn't she?? LOL

I've posted a recipe a while back called " Homemade Dulce de Leche" recipe was passed on to me from my Aunt in Argentina, takes a little time to make but is very simple & very yummy.
Enjoy

this is awesome boiled 2 cans last nite for 3hrs open this morning really yummy getting ready to frost this on a white cake

my husbands family calls that condenesed milk pudding we boil for 5 hours than slice and place a pinapple ring and homemahe whip cream on top yummy yummy

Geez, I'm glad I found this post..now I will go and delete mine.. I also want to know about the adding the boiled carmel to buttercream..How is the consistancy and the taste? I love caramel and have known about the boiled can but was trying to make more work for myself I guess...

ok, new problem...the cans say not to boil unopened..? Do I do it anyways? and what about the dangers of boiling metals?

It's ok to boil in the can, JUST MAKE SURE IT'S FULLY COVERED WITH WATER THE ENTIRE TIME!

The carmel turns out WONDERFUL! However, I didn't think I could frost with it (to soft) so I added a couple of cans to a 1/2 batch of buttercream. Not a good idea! It was way to soft but I didn't want to add anymore powdered sugar to it to stiffen it up because it was already way too sweet AND it was loosing that rich carmel taste. I put it on the cake anyway and it wouldn't even hold the layers on, they wanted to slide off! So I stuck it in the fridge.....looked ugly as all get out, a BLOB...but BOY was it good! I think I'll stick to using the carmel as a filling with a good stiff buttercream border to hold it in!

It might make a good ganache, however I have no idea how you'd go about doing that.....

For all of those asking about the crockpot version of this, I did a search and found this from Southern Living:
http://findarticles.com/p/articles/mi_qa3676/is_199603/ai_n8741584

It is actually for making a pie (which sounds delicious BTW), but the caramel cooks in the crockpot. Hope this helps!

I boiled 4 cans for 5 hours & got perfect results.  I removed labels from sweetened condensed milk, set them on their sides in a big thick bottomed pan, covered them with hot water to cover at least 1" over the tops of cans, and covered with a lid. Simmered them for 5 full hours, monitoring water level, adding water as needed. Let it cool in the pan overnight (I'm very patient), and next day I opened one can to find ooeeyy gooeeyy caramel.  Still have opened can in fridge (minus small tasting) & 3 in the pantry for future use. It was almost too easy, but not quite as good as the regular caramel I've made before, the one where you cook sugar till browned & add cream. Thats a more volatile process but very good, and there are options that make caramels you can cut into squares, etc. 

AI know this is a really old thread. I tried boiling the milk in the can and it was okay but not great in my opinion. I just wanted to share this one with anyone that might stumble on here. Go to joy of baking website and look up alfajores. It is more labor intensive but definitely worth it.