i found this dell optiplex 755 in a scrap yard perfectly functioning{came with side panel just have it off} its ungodly slow with only a single stick of ddr2 2gb ram and
Dell Optiplex 755 Motherboard | Laptech The IT Store.
Dell Refurbished OptiPlex 755 Desktop Intel Core 2 Duo 2GB Memory 160GB Hard Drive 755 DT-0184 - Best Buy