My laptop is a Dell Vostro 1500, about 2 1/2 years old.

 When the AC adapter is plugged in, the battery light flashes an unceasing pattern of an amber light three times followed by a solid blue light.  The hard drive light does the same thing but with less light intensity.  This happens when the computer is on, whether the AC adapter is plugged in or not, and also when the computer is off but the AC adapter is plugged in.

Does this mean that the battery merely needs to replaced or could it be something more serious?  I recently reinstalled my Vista system because the system was freezing and crashing before.  It's been working fine since the reinstallation with only one crash (which happened when I had several large programs open and was working on a large audio project).

Any help would be greatly appreciated!