I am having trouble how to remove the hardrive from the case one of the screws is stucked into the case

I think you know what you gotta do...you gotta get that screw out! Not much we can do to help ya with that. You either need a good screwdriver, or a small socket...if the threads are stripped & it just spins without backing out, you'll need to somehow pry it while turning the screw, or if you can, grab it with a small pair of vise-grips & pull on it while turning it out...

If the head is stripped, you can get a "screw out" at sears that digs into the head of the screw.
Another option is to take a drill bit the size of the screw shaft. Drill into the screw head, and the head will snap right off.

When all else fails, beat the %*#$! out of it!!!

The screw that is installed is probably the wrong size or thread pitch. It is stripped. Use a pair of pliers and turn and pull together. When reinstalling that drive don't use that hole again.