Yes that will work in your motherboard. The 1900+ runs a 1.6 ghz, while the 2400+ runs at 1.93 ghz. Some say that this is not the best of upgrades, but it will help. Not everyone needs a high end gaming machine.
Obvisuly a motherboard, CPU, and RAM upgrade would be far superior, but I still think the 2400+ will help. I recently did about the same thing, I went froma 2500+ to a 2800+ (yes a little different, and I did it becuase I was able to sell the 2500+), I saw a difference.
$50 really isn't that much for an upgrade. I've spent that much on a heatsink, just to drop my temps a couple of degrees. If you don't do much serious gaming, and an upgrade is a little ways off, I think the 2400+ (especially since it relatively cheap), would be a good investment.
My Desktop: <A HREF="http://Mr5oh.tripod.com/pc.html" target="_new">http://Mr5oh.tripod.com/pc.html</A>
Overclocking Results: <A HREF="http://Mr5oh.tripod.com/pc2.html" target="_new">http://Mr5oh.tripod.com/pc2.html</A>