Do you mean no lights come on at all ?
Or it doesn't boot ?
If lights doesn't come one, check your power cable
turn off/on the power switch in the back of the computer,
if it doesn't help then most likely the power supply went bad.
I would take it to a local computer shop, they can fix it
while waiting.
Check to see whether there are any signs that the machine is getting power -
does the power supply fan come on? any lights? noise? If not, the most
likely culprits are failed power supply or broken switch.