If your Gateway M675 laptop is displaying a blank screen, and continues to do so for an extended period, there's likely either an error that has frozen your computer, or it's off. If the screen is black, you'll need to troubleshoot power issues. If not, the best way to fix this sort of error is to restart your computer. You may be tempted to simply hold the power button down to perform a hard reset, but that is not the best course of action, as hard shutdowns can damage your hard drive. Instead, try a few keyboard shortcuts to see if you can resolve the issue or at least shut the computer down gently.