Securing French Bi-fold Doors to Wall

I need to put down a threshold from carpet to hardwood which both are on a concrete slab. The space in between the carpet and hardwood is about 1/4 inch. The threshold I have has the holes in the middle for the nails to go and of course it hits in the space where the slab is. How do I put this down on the slab? The nails just bend and don't go in the slab. Thanks Sade

Hi All, At the end of March we moved into a a house built in 1985. In the living room is an arched (don't know the term really - a 5 window bay?) window. We repainted the room and insodoing realized that it is the only window in the entire house that was not replaced a few years ago - the house has all new argon-filled windows - except for these! We also noticed that they look like they are double-panedglass - 5/8" thick, 5'x18", and probably home installed (like everything else the previous owners did). When we were painting we realized that the atrocious dark teal paint was beneath the messiest non-paintable silicon job we had ever seen. It has gray mold growing under it. Also, the 3/8"x1" trim holding the windows in place (is there a term for that?) was rotting in places. In May, we started removing the trim and silicon, with the idea of replacing it. It got put off when spring came (there was a garden to plant), and then I had a baby and it got put off longer. Well, now it's December and we noticed that after the -20C weather we've been having that there was at least an inch of ice around the bottom and sides of the windows. My obvious question is - what is the best way of re-framing the windows? What is the best way of decreasing the condensation on the windows? Is the wooden 3/8"x1" enough? (I doubt it) Can we put in expanding foam around the window and under the wood - would that work to cut down the condensation? Should it wait until spring when things are warmer? Obviously I know little about these things. My original plan (in May) was to simply replace the wood. Now, however, I know there is a bigger problem that needs to be addressed.