Dell Studio 17 not charging

I have a Studio 17 have had it for about 2.5 years. A couple of months ago I started getting a message saying I had the wrong adaptor plugged in and needed a 90W one. The battery is now at 0% and everytime I start the computer I get a message telling me my AC adaptor is less than 90W and I need to connect correct one. I have to press F1 everytime to get the computer to start up with "wrong" adaptor. The thing is, I have had the same adaptor the whole time so why now is it saying its wrong. I have tried a new battery and that didn't work either.
What can I do?
No longer under warranty so if I had to take it to a computer repair person roughly how much would it cost to fix?

Reply 1 : Dell Studio 17 not charging

At 2.5 years the 300 CYCLE battery may be indeed be gone. A failing battery could overtax the power brick so for a test, try it without the old battery.

BUT FIRST try the old reset trick. Remove the battery (and brick) then hold the power button down for 10 seconds. I hold it down for the full minute. Let go, install battery, brick (adapter), count to 10 and try it again.
Bob

Reply 2 : Dell Studio 17 not charging

Do I turn off the computer before removing battery and brick then doing reset?