How to loosen battery screws?

What I've done before is I'll put a little extra pressure on the chassis, but the problem with that is if the LCD is attached to the laptop, it's very risky -- granted, I've never broken an LCD doing this because I take precautions and know when to back off, but these Dells aren't cheap to replace it on if you break it since you need the assembly for the XPS -- granted, the Latitudes with the "normal" bezel can have the screens serviced but it's a pain and cost is similar to a used assembly so they are also "assembly swap" in practice, but not in design. That said, unless the connector is on the battery where it has to be removed, you usually just need to disconnect the battery on these laptops.

Best ways to do it are to put something soft on your desk, open the laptop (hang the LCD on the edge to avoid damage, and cover it to avoid damage) and turn the screws until they budge.
However, it's VERY, VERY IMPORTANT you match the bit size as this can strip the screw if the driver is too small!

If that doesn't work, the larger handle in the Manta driver kit works wonders on these screws (not just Dell).