I can't remove my iphone 4s screws at the bottom, regular 5 star screwdriver wont work. Are they stripped?

I'm not sure why you would want to remove the screws, as doing so voids your warranty. Do they turn, or can't you turn them?

If they were stripped they would turn but not come out. You may need a good quality driver and more force; they probably put locktite on the screws so they don't vibrate loose.

Not to be cold, and please don't take it too personally, I don't know you from Adam and this is the interweb tubes, but I have to observe that if you can't figure out how to get the screws out, maybe you should re-think opening the phone at all if you ever want it to function again.

There is no such thing as a "regular 5 star screwdriver". A regular star screwdriver is most often considered a Torx screwdriver, this has a 6 point star. A Torx will not fit iPhone screws. The bottom screws on iPhone 4S are proprietory Apple Pentalobe Screws, sometimes called pentalobular or pentacle. They are easily removed, never stiff like they are with the iPhone 3G or 3GS, these come out with little force. But you have to use a Pentalobe Screwdriver. Not recommended, but straight edge tools that correctly fit across the screw head depression will work.