Rachel, you can resize it...All you have to do is resize your photo down to under the 500kb maximum allowed on RootsChat. Do this in your photo editor (Microsoft Office Picture Manager or whatever you are using). Go into the edit functions, choose resize, shrink it a bit then save the changes and see how big it is now. Repeat until it's small enough.
Don't use the compress feature, though. Resize.
If you're still having trouble, and have read Cazza's scanning tutorial, you can PM somebody for help.
Cheers,
China