What happens when you don't use a high enuf wattage power supply?

[gourmettea]

I would put this question in highly technical but I think this is a pretty basic question.

 

[Electric Amish]

Your computer won't boot or it'll shut down/reboot randomly.

 

[slycat]

it might work for a while...then have problems and may break faster...or u see anomalys.