It will make it easier to help you w/ your problem to know the exact model, size, year built, RAM installed and OS you're running.
"They fixed it two days ago by resetting it"
What kind of reset?
Normally it would be this:
Reset SMC
http://support.apple.com/en-us/HT201295
Which is what you did?
They might have done this:
Try a hard reset. Disconnect the battery (open the bottom and pull the connector off. Use your fingernails.) and power adapter. Press the power button for 1 minute. Let the computer sit for 5 minutes, Reconnect and try to start up.
No? - Go through the same procedure and try to start without the battery connected.
The addendum to this would be to try a known good battery.
This would be for a "no start" scenario but basically it's the SMC reset w/ a battery you can remove.