Hp slim line s700n beeps one short, one long when powered on

One Short followed by one long beep is indicative of a Memory problem. Unplug the power from the slimline. Remove the case to expose the inside and wait about a minute to make sure no lights on the motherboard are still on after unplugging the power cord. If you have more than one memory chip installed try removing one of them and sit it aside. Leave the cover off, plug the power cord back in and try rebooting. If it doesn't boot unplug the power cord, wait till all lights on the motherboard are off, then move the memory chip that is already in to the other slot that was occupied by the memory chip you have set aside. Plug the machine back up and try rebooting. If you still have a problem remove the memory chip and set it aside, now do the same thing with the initial memory chip that you set aside (that is trying it in both slots to see if your computer reboots). If you get it to boot successfully, make a mark with an ink pen or felt pen on the chip that is set aside because it is probably bad. You can try placing the chip you marked on back in with the working chip and see if your computer boots. If it does, it simply means your computer's memory just needed to be reseated, if it does not boot you know for sure the marked chip is bad so leave it out and take it (the chip, not the computer) to a repair shop to buy another chip.