I need to replace the power supply plug in my hp ze2000 laptop, i have all of the screws out of the bottom of the computer but can not get the case to open. How do I do so?

First of all remove all your components ie. RAM, hard drive, battery, CD/DVD drive etc. Sometimes there are screws located in the area where these components are located that secures the top and bottom halves of the case.
I suggest that as you remove the screws from the bottom of the case you take a note where the came from as some of the screws are different lengths.
There may be s strip panel between the top of the keyboard and the LCD screen, remove this first, it will be clipped in place and held with screws from the bottom of the laptop.
Next the keyboard should removed and keyboard cable.
Look closely for screws hidden behind plastic stick on covers, you need to use a sharp thin blade to lift off these covers to reveal the screws behind the covers.
The top and bottom halves of the case is usually held in place with plactic clips, start at an opening and carefully pull apart until a clip releases and the work along that edge to release more clips. Continue along each edge until you separate the case.
The LCD screen is usually secured with screws on the back edge of the laptop and possible with screws near the edge of the motherboard. Take care to disconnect the video connector.
The motherboard needs to be removed from the bottom half of the case so you can access the power connector.
Take careful note where you remove each screw as you need to put them back in reverse order.

Best of luck, have fun.