Every video I play is way dark, sometimes so dark it's hard to see. This happens with WMP, Winamp, Creative MP, even Netflix instant views are dark. Seems like a simple thing that's causing all videos to display dark. Anyone know why or how to fix it?

Have you installed/updated your graphics drivers? Has this problem been there since the system was new or did it happen recently? Any recently installed updates? I would also mention that running XP on a machine with only 256mb RAM is a recipe for trouble. Do you have a separate graphics card or are you using the onboard graphics with shared ram? It seems Dell did sell these units back in 2003 with XP so there should be appropriate drivers available. Do you have a spare PCI slot? If so I suggest you consider getting a PCI graphics card ( Sometimes hard to get but your local PC market might be a place to look) and also look to install more RAM. You have 2 slots that can take 512mb each. Goin' Fishin' (Some day)

Well, if its happening across the board on all media players, it would tend to point to a problem with your graphics card or graphics drivers. I'm guessing the problem exists on the various video sharing sites too? Like YouTube, MySpace, Google Video and etc? What graphics card do you have set up? Try updating the drivers on it if possible, although as mentioned above, it would help to know whether the problem has always existed or has only just arisen. If it's always been a problem, you're probably looking at a hardware problem of some kind. The Definitive Guide to Registry Cleaners & PC Optimization

I searched around computing.net last night and was able to disable "overlaying" in 2 of the media players, and the video brightened up. I don't even know what "overlaying" does - says it's supposed to improve video quality. By making it darker, I guess?

There are usually 'Overlay' adjustments that you can tweak. Go to Display Properties > Settings > Advanced and scan through the options for an 'Overlay' brightness setting. Note that you normally have to be using 'overlay' at the time you try to make any adjustments.