My laptop flashes but won't start

Check and reseat the RAM.

Unplug your computer and remove the battery. Then remove the 2 screws that hold the bottom cover on. Slide the cover forward and remove it. Next unplug the cmos battery, it looks like a black button about the size of a quarter. Press and hold the power button for 8 seconds, then wait an additional 5 minutes before plugging the cmos battery back in. Reassemble the computer then power it up. This should take care of the issue. Make sure if it does boot up normally after this procedure that you reset your date and time. Otherwise you will not be able to receive important updates or use your browser. Hope this helps...