On start up I had a message which said for emergency start up press F8, I think it was, and it did it for me. It must be easy because I managed to do it. I didn't need any discs it did it all automatically all I had to remember was to copy everything I wanted to keep, to a memory stick.
I used to remember the good old days when Microsoft gave you a proper disk so you reinstall your operating system.
These computers usually come with a restore partition that allows you reinstall Windows automatically. If you don't have that then your going to need to buy Windows or ask your manufacturer for a rescue disk.
Without getting to complicated, if you can get hold of a Linux distribution, you can run Linux from the DVD. Once the Operating system has loaded you can and get access to your windows drive so you can transfer all your documents to an external drive before wiping the machine.
Its something like, turn it on and immediatley start pressing F8 repeatedly until it goes into the restore function. Failing that, press F1 or F2 during start up (it should tell you on the bottom of the screen when you turn it on) then select the restore option.
This will boot your laptop from the image in your back up folder on your hard drive