AMD cpus have a cam lock type cooler. You may see 4 screws, but those are to hold on the brackets(sometimes one part sometimes 2 parts depending on the board) plastic tabs that the cooler grabs onto.
As the above user wants to know, the width of the case plays a role in what coolers you can use since tower coolers are rather tall sometimes.
Now if you just have a failed fan, you may have 4 fan screws in the corners(they can be used on the replacement fan). The fan is a 70mm x 70mm x 10mm or 15mm thick fan(I have seen both on various AMD coolers). They are not too hard to find, but the stock one is VERY fast(at top speed), so slower fans may not cool well enough for some systems.