is there any way to place a scroll over effect using gimp? like a pic goes from normal colors to negative when u scroll over it.
no. The only way that would work is if you used the key short cuts for it (which I don't even know if there is any) and you moved the mouse over and pressed these shortcuts. Otherwise, no.
I'm pretty sure you could do that in Flash. A friend of mine once made a dark cave-looking signature in Flash where you could rollover the mouse onto it and it would illuminate the signature to show his name, just like a flashlight.