I recently noticed that the screen on my Dell Inspiron 4150 was loose and wobbly. That was a big concern, since at the time it was my primary computer. I paid $9.95 to download Dell's repair manual, took the computer apart, and then discovered that I didn't need to.
So this page is here to save you from the same fate—especially because there are lots of risks involved in completely removing the display. (My display isn't loose, but now my keyboard rattles!)
Here's the secret: the display hinges are secured in two places. On the body of the computer, there are five screws (use a #1 Philips screwdriver) labeled "D". Make sure they are tight. (They were on mine.)
On the display, the hinges are held together by the same screws that clamp the bezel to the LCD screen. They're hidden by two rubber bumpers on the lower left and lower right of the screen. Pry the bumpers off with your fingernail, tighten the screws, and voila! Your display has been fixed. The bumpers will stick back on with the leftover adhesive.
Brian Huber has offered the following advice on repairing a Dell B130 display:
On the back panel of the computer there is a screw directly under each hinge. Simply tighten them up with a small Phillips and the hinges are tight again.