E1405 died in use. Won't restart

My 4+ year old E1405 with 160GB drive, 2GB ram, Windows 7 shut down on me while in use for no apparent reason. The machine will not restart. No boot up, no sign of life other than the power light coming on briefly then goinb back off. If I hold the button down, the light will flash. No signs of life! I tried a different battery. Tried power supply alone. Pulled Hard drive, RAM, CMOS battery etc and put it all back together but still no life. Any advice? Thanks in advance,

Hawk