F8 shouldn't do anything for this type of error, it was likely clearing CMOS like suggested above, you may need to reboot twice and give it a minute to load after clearing CMOS. 
Hello, I changed some Alienware Command Center settings and rebooted my PC for them to save. The PC turns on but there is no video output. The Alienware Head flashes white once and then white twice. I’ve already had a similar problem once and I solved it by pressing F8 when turning on the PC. It doesn’t work this time though. Any suggestions please?
Aurora R10, AWCC reboot, no video