If the backplate is removable, then a micro atx board should fit. But if the board snaps in place without screws, then I wouldn't try it. The dell case is too old to salvage, and you will definately want to upgrade the power supply. Newegg often has rosewill atx cases for only $20-30 shipped, and they won't have any limitations for mounting a new board. And you should list a budget that includes new ram if you want a real upgrade. Trying to change boards using your old ram won't gain you any performance.