The manufacturer should be able to provide you with a system restore disc (discs), maybe for a fee or not. You will need to use the activation key from the label affixed on the laptop.
I am afraid that without a OS disc you will not be able to solve this, if the registry has been altered by some software and is causing this behavior the only way to restore it to defaults is to do a repair of the OS installation. For that you'll need an image of the laptop (restore to factory settings) or at least a OS disc (to do a repair of the OS only). If you can launch the factory restore process that came with the laptop, you'll lose all the settings and programs that you put on it afterwards, but at least you'll have a working PC. After that (if you decide to go this route), make sure you create a restore image from the system as you like it and store it on a separate drive, along with the OS activation key ( in case the label becomes illegible).