Most, but not all, boards have a facility to clear the CMOS memory. Usually it's a set of 3 pins with a jumper, it may be labelled something like CMOS_CLR, and with the power to the system off, the jumper is moved from its current position to the adjacent pair of pins for 5 seconds or so, then returned to the original position. (ie, if normal position is across pins 1 & 2, the clear setting is across pins 2 & 3). Some more recent boards have a small pushbutton mounted near the battery. But for a few boards the only way is to remove the battery for a period, occasionally this needs to be up to a period of hours.
The purpose for clearing the CMOS memory is in case either the memory contents has become corrupted during the flash process, or changed features of the updated BIOS requires more or different data and the old CMOS data is no longer correct.
If you respond to hamluis' request for system or motherboard model information, we can be more specific. Also, if clearing the CMOS has no effect, it will also help to know things like the exact flashing procedure you followed, the source and filename of the BIOS update if you updated manually so we can be sure if the correct update was used.
Also, when you say you hear the computer running, do you just hear fan and drive running noise, or do you hear a startup beep, see drive access light flashing, hear Windows startup sound? These will indicate different fault conditions, for example, if you hear the BIOS beep but get no display, maybe onboard video has become enabled and is clashing with a video card, it may be necessary to remove the video card, boot up using the onboard video, turn it off again in the BIOS setup, then shut down and refit the video card.
Edited by Platypus, 27 February 2008 - 07:28 AM.