I read through the above posted thread, it seems you were able to charge after using the old power adapter? Are you still having issues? In my experience dell computers are one of the more picky laptops in reguards to OEM power adapters and batteries.
You can check in the bios if the power adapter is recognized or not. Right after powering on the laptop start tapping F2 repeatedly until you get to the bios screen. Use your arrow keys to highlight the power options and in that screen you should see if the battery is recognized (I suspect it will be since you mentioned it did charge before), and then if the power adapter is recognized. If the power adapter is recognized it will say something like 65w or 90w which is the wattage of the power adapter. If you see power adapter "not recognzied" you either have a bad power adapter or a bad jack in the laptop.
The first step before taking the computer apart is to try with a new or known good power adapter (one that works in another computer), if that adapter is still not recognized you likely have a problem with the jack built into the machine. You can visually insepct the jack to see if there is any obvious damage to the center pin plug this is what carries the signal for the computer to either recognize the adapter or not. If the adapter is not recognized, the computer will run from the power adapter (if the other connections are ok) but will not charge the battery. This is a saftey feature to prevent overcharging and potential fires.