Before you go for the BIOS battery, TG, give all the connectors a good checking. You can get this effect if the BIOS is set to halt on any errors; so a loose connector anywhere can stall the boot. And depending on the BIOS brand, it may or may not give a beep code, or pop up an error message. And that goes for checking the internal connectors, as well. A loose floppy or HDD connector can halt boot, just as a disconnected keyboard or mouse will. If that doesn't work, -then- go for the BIOS battery, or find the jumper to reset the BIOS to default state. If that fails, then disconnect all the internal drives save for the boot drive, and try again (this -should- force a device update in the bios table, getting you into the bios to work with the settings). If that fails, then pull the mouse and try it again; unless something is wrong, that will almost always force an error and bring up the bios. Worst case, pull the power lead on the boot drive. That =will= force the BIOS to choke out error and bring up the access screen......

Unless something is wrong with the motherboard.