Optiplex 960 w Intel Series 4 chipset screen too dark

My graphics card was going bad so I removed it and switched back to the onboard graphics chipset on my Dell Optiplex 960 MT, running Windows XP.  Now I'm finding some videos, especially with dark backgrounds, are too dark and it can be hard to see things sometimes.  I've checked the monitor adjustments (Samsung 220wm) and the brightness is at 99 so there's no room for change there. 

In Device Manager/Display Adapters,  I find there are two instances of the Intel 4 Series Internal Chipset.  I don't know if I should uninstall one of these or just leave them alone.  The chipset driver (in both is 6.10.14.5420 dated 7-23-12).  I downloaded the latest driver(s) for this computer, installed it, but it didn't show up in Device Manager, so I'm still going with the original driver and not sure if the newer one would make any difference anyway,

I'd like to know if there are any adjustments for the on board chipset.  Is there software that would allow me to make some adjustments to improve this dark screen problem? 

In the meantime I'm looking for a used Nvidia GTX 750ti graphics card, or something that would give me optimal capability for video(I'm not a gamer) and have WinXP drivers available.  But I'd like to fix the current problem first.