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
A-Tech 8GB (4X 2GB) Max Memory RAM Kit for Dell OptiPlex 755, 745, 740, (MT, DT, SFF) - DDR2 667MHz PC2-5300 Non-ECC DIMM Upgrade at Amazon.com
√ Simpaticotech™ Dell Optiplex 755 Core 2 Duo E8200 2.6GHz 4Gb Ram 160Gb DVD±RW Windows 10 Professional Tower | 30 giorni di prova gratuita - media voti 0 / 5 - Ricondizionato Rigenerato Prezzo Offerta
8GB (4GBx2) Team High Performance Memory RAM Upgrade For Dell OptiPlex 755 Series (Desktop Mini-Tower and Small Form Factor). The Memory Kit comes with Life Time Warranty. at Amazon.com
8GB 4x2GB PC2-6400U DDR2 800mhz RAM For Dell OptiPlex 755 760 960 XPS 410 420 AB | eBay
Dell Refurbished OptiPlex 755 Desktop Intel Core 2 Duo 2GB Memory 160GB Hard Drive 755 SFF-0430 - Best Buy