This guide will help you with the replacement of the battery in Aspire 5100 laptop. The battery replacement is very easy, and shouldn't take more than a few minutes. You will need the correct replacement battery for your laptop to complete the installation.
Flip the laptop over so the audio jacks are facing you.
Unlock the battery by sliding the button (located above the battery) towards the outer edge of the computer. When you feel the battery release and pop up, gently pull the battery from its compartment.