How do i reinstall my windows 7?

I have w7 32 bit operation and i have a directX bug that made my graphic card work from pixel shader 4.0 to 1.1 or 1.4 but when i try to install a new directx and overwrite the old one i get an error that needs to be fixed by uninstall my w7 but the problem is i have never done it before and i lost my disc i got with the laptop so i would appreciate me like step1. step2. .........etc how do reinstall my windows 7 without disk and how to find the drivers after the install PLEASE i don't have much money so i need to do this by myself i have directx11 (it was installed when i got the laptop) and if you know another easyer way to fixing pixel shader error my graphic card is ATI Radeon HD 3200 if you need to know anything els i will add more information