On an Inspiron 9300 or 9400 They're M2.5x4mm machine screws. I have bunches of them, but I get mine from Dell and I also purchase some stainless steel ones from an industrial supply company. I think parts people have screws available for most Dells.
Thanks for the info, but I may have been misleading with my sig. I'm actually looking for Inspiron 5100 LCD screws for my little brother's laptop. Anyway, I'm going to parts people to find out. If you have any other ideas let me know!