Dell Studio 1747 - Slow CPU, Can't charge battery

Hello guys, I'm new here and I think this will be the best where I think I can finally solve the stupid problem I have. So here's the story.

Specs : Studio 1747, Core i7 720QM up to 2,8Ghz, 8Gb of Ram and ATI Mobility Radeon HD 4650

A year from now the battery of the Studio 1747 wasn't charging, the dc jack inside started to be loose. I had the "Pluged in, not charging" and "AC adapter cannot be determinated" errors. So I was like okay no problem, I'll just buy another dc jack. So I replaced it but the battery wouldn't charge. It was frustrating because the CPU clock of my laptop was highly affected ( down to 900Mhz ) and playing games was and is again impossible. It lags sooo much.



Over the time I changed the battery because the old one was dead, when I press the button to check the battery life, I get the three light of death. So I got myself a new battery, it is detected by my pc but it wouldn't charge. So I'm like okaaaay, I then get myself a new motherboard and a new AC adapter but still no success.

WHAT THE HELL IS WRONG WITH MY LAPTOP

One of the solution I thought was to mod my BIOS so I can change the CPU clock speed back to normal and I can't do this alone so I don't know.

I'm in digital media at school and we use a lot of video editing and 3D softwares but I can't do anything because the clock speed is too low and it lags.

I really really really really need someone to help me, I'm buying a new pc in June ( waiting for Haswell ) but I really want to survive those six months with my current laptop.

 

So let me get this straight: you have changed your motherboard, DC jack, AC adapter and battery and you are still getting the "ac adapter not detected" message in BIOS?

 

Yup. I've changed everything related to it and I still get the same error and I've flashed both motherboards the lastest BIOS update :/