Is there any way to update my graphics card while my computer doesn't work?

I'd first check to see if it's not the monitor going crazy. Even with a bad driver, windows should default to a basic VGA driver unless something is actually broken. I'd try with a different monitor. If it doesn't fix the problem, return it. You may have a bad graphics card as well, but you are right, it's difficult to isolate a bad driver. You may even want to try booting windows in safe mode (which uses that default VGA driver) by tapping F8 as soon as the BIOS starts loading (right after you turn the computer on, but before the windows screen starts loading.)