No lights is not promising.
Only thing to try in such case is to remove battery, wait, and reinstall battery. This resets the radio which might hang and lock up system.
There are XO community repairs centers where low cost repairs can be obtained --- do you live near one:
This is an index of repair topics. Look at repair centers.One other possibility:
If you have a computer from 2007, there was a problem related to the internal (watch style) clock battery. There was combination of an out of spec battery holder and a bug in the firmware. The battery could be jarred out of the holder. Even if the battery was replaced, the firmware would wait for the clock to roll over and XO was effectively "bricked" --- no lights -- not power up.
This required a special connection to the internal serial port to advance the clock. It was also possible to wait a month for the clock to roll over.
Some of the repair centers can easily correct this problem. Later versions of firmware eliminated this bug.