Is your laptop battery not charging?
This can be something really simple, but it could also indicate a very expensive problem to fix. Let's start with the simple solution:
Sometimes all you need do to fix this situation is to reboot the computer without, then with, the battery. Shut down the laptop, unplug the AC power, and remove the battery. Then plug the AC power back in and boot the computer. Then shutdown the PC, unplug the power adapter, and reinsert the battery. Plug the AC power back in and boot with your fingers crossed. Hopefully, your battery will start charging.
Didn't work? Okay, it was worth a shot. The next fix is a little more complicated. It's based on the assumption that a necessary driver may be corrupted and needs to be reinstalled.
First, you need to get to the Device Manager. If you're using XP, click Start, right-click My Computer, and select Properties. Click the Hardware tab, then the Device Manager button. If you're using Vista or Windows 7, click Start, type device manager, and press ENTER. (There are times when I wonder why anyone prefers the XP user interface.)
Once you're in the Device Manager, expand the Batteries section by clicking the + or the tiny arrow to the left of the icon and word Batteries. Right-click Microsoft ACPI-Compliant Control Method Battery and select Uninstall. Verify that that's what you want to do. Do not uninstall any other drivers.
When the uninstall is complete, select Action from the menus on the top of the window, then Scan for hardware changes. When the scan is complete, the Microsoft ACPI-Compliant Control Method Battery listing will reappear.
If that doesn't work either, your battery is almost certainly dead. They do wear out.
You only have three options here, none of them ideal.
1) See if you can buy a new battery for your model. Check first with the manufacturer, then search the web. Remember that you need one specific to your laptop's model number.
2) Accept the fact that your laptop can now only work where you can plug into AC power.
3) Buy a new laptop.
Whichever course you take, make sure to dispose of the old, dead battery properly. Check for battery recycling in your area.