|This kind of troubleshooting has been described here hundreds of times. Your powersupply may have failed. Just because fans spin that does not prove the PSU is still fully working.|
If you have access to another powersupply, that's your starting point. Without a known good PSU you cannot confirm what other components might have gone out.
Once you have a good PSU, strip the system down to barebones. ie: disconnect all power & data cables from all drives. Take out all but 1 stick of RAM. Disconnect all usb devices. Leave only motherboard, CPU with heatsink fan, 1 stick ram, PS/2 keyboard, and graphics. Use onboard . Now connect power and try to boot into bios.
Any display? Any POST beeps?
Goin' Fishin' (Some day)