Try to be a bit more descriptive, did you make any changes to your computer's bios recently other that the boot priority? Has anything damaged your PC recently? How old is this computer? Has there been any other issues as well?
The best I can tell you is to look up a video on how to remove your CMOS battery, (looks like small silver button) which will reset your BIOS to default settings which may help. Make sure to remove your laptop's main battery before you do so, then hit the power button a few times to discharge the laptop of any residual charges. After the CMOS battery is out, wait 2 minutes and reinsert the battery, and close up your laptop. plug yourself into a wall outlet just for good measure and try booting up. If this problem persists then it may be something to do with your hard drive. Please comment back here once you have tried the battery removal solution. If it is your hard drive you may need to re-install windows.
