almost all the desktop case seems to be from a Dell Dimension computer, wich one? no idea, almost all look the same.
it cant be from the 2000 line as the fronts of them dont match, nor the 3000 line as most of them postdate CSS with the exception of the dell dimension 3000, but its front doesn't match.
it can't be a 4100, 4200, 4300S, 4500S, 4500C, 4600, 4700, 8100, 8300 or an 8400 as none of them match the front cover.