The Dell OptiPlex GX280 computer comes in five different form factors with three different, but similar, methods for removing the case. Identify whether you have a "Small Form Factor," "Small Desktop," "Desktop," "Small Mini-Tower" or "Mini-Tower" system by clicking on the link in the "Resources" section of this article. There are three opening methods for Dell OptiPlex GX280 towers, and the method you choose is dependent on the type of tower you have.
Unplug the cables from the back of your OptiPlex GX280. Wait at least one minute before opening the case in order to allow the capacitors inside to completely discharge any electricity. Set up the case where you have room to open it, such as on top of a desk.
Open the "Small Form Factor" and "Small Desktop" cases by locating the two release buttons, which are located near the back of the computer on the narrow ends. Press them at the same time, then lift the side of the case up. Pivot the back of the case up toward the front.
Open the "Desktop" and "Mini-Tower" cases by setting the computer down on its side so that the release latch is facing up. Slide the latch while you lift the side of the case. Pivot the side until it comes free of the anchor points, then lift the side away and set it aside.
Open the case of the "Small Mini-Tower" by setting the computer on its side, ensuring that the power cable port is closest to the ground. Press the release button on one side of the computer, then lift the side with the other hand. When the first release button is free, press the release button on the other side and lift the side of the case to free the second button. When both release buttons are free, hold down the case while you lift the side of the case off.