My laptop only works with a power adapter even when the battery is full. (Xp)
As soon as I unplug this he goes out.
Why is that?
I see that XP is installed on the laptop. This means that the laptop has been around for a few years. Lithium-ion batteries tend to be defective despite the battery level being full. Often dependent on age. That is probably the case here. So the battery is defective.