Laptop battery icon says "plugged in, not charging"

I have a Dell Inspiron 1501 that is running Vista. It still has the original battery but I did have to replace the AC adapter about a year ago. I replaced it with a Targus that is intended for use with this system. It has worked without an issue until a day or so ago when I began seeing that the battery icon when moused over showed the message "plugged in, not charging" with the battery showing 15% charged. The computer runs fine when plugged in but cannot charge it. Also tocday I started getting a message that the computer could not detect the AC adapter when I started the computer. However, the computer is running off of the AC right now and for the last 4 hours without issue so it has to be detecting it. I have tried to remove and insert it back into the computer and I have tried to uninstall and reinstall the driver for the battery which is a solution I found on here without success. Any help that can be provided would be greatly appreciated. Thanks

Greetings,

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Technical Support for Inspiron 1501 Problems Charging a Dell™ Inspiron™ Battery