I Need A New Battery For My Laptop Don't I? :/

[Steel _R a i n d r o p s]

I have a Dell Inspiron 15. I've had it since may 2009.

I have my computer plugged in, and it's not dying, but it isn't charging either. It Says Battery Level: x% Plugged in, not charging.

This has happened before and I either unplugged it or shut it off or it fixed itself or something. But yesterday, it said battery 0% Plugged in, not charging. It has said that for like a week. I normally just leave my laptop on sleepmode, and the white charging/power light is usualy on. So I did that as normal last night and it started going from soild white, to flashing orange/red-What it looks like when its dying, then back to white. It did this all night. I looked at it in the morning and it seemed fine. Before it started to blink orange/red, I could unplug it for a couple seconds before it would die. While the light was like that, the second I pulled it out the slightest, it shut down. I left it off and unplugged during the day and when I got home and plugged it back in it still did that. Now the light is back to normal, soild white. But the battery level is now 10% but it still says not charging.
So I'm thinking I need a new battery, or I need a new adapter.
Could you tell me which and about how much it would cost?
And if you could explain the light mess that would be a help too!
Thanks!

[Kwaru Nagisa]

Probably the battery they tend to burn out far more the the power supply by far,

[Ender91]

You can't leave the laptop plugged in all the time, that's what killed your battery, make sure you run it down at least 2 times a week and that will help your battery survive for years, as for a replacement, check eBay or newegg.com for one, it should cost $30-50 dollars

[Steel _R a i n d r o p s]

Your probably right about that. Now I HAVE to leave it plugged in.
I tried not to leave it in that long.
Overcharging burns your battery.
I think I did that to my phone lol

I went on to Dell's support thing and it said something about downloading a BIOS or something, so I did that but it said I need a greater than 10% charge to run it :/ That helps me so much lol

[Steel _R a i n d r o p s]

neutral neutral neutral neutral question question question question question question

So, I turned my computer on, the batter was still at 0% andnot charging. I went and played a computer game, then i went and read and now it says battery 88% CHARGING. I'm afraid to unplug my computer incase it stops.
Thats so weird, why is it doing that?