Here are a few tips. PB blast let sit. Go raid the cleaning supplies for a little Ajax's cleaner, or any dry household cleaner that has grit in it. Use liquid medium of choise on end of screwdriver. I use spit. Apply cleaner to screwdriver tip and work into screw head. Try tightning the screw just a little, dont snap the head off, but try and get it to turn a little. If it moves reapply spit and cleaner and slowly work screw in and out. If all that fails heat, grind, destroy as nessecary.