OFFTEK 2GB Replacement Memory RAM Upgrade for Dell OptiPlex 755 Series (Desktop Mini-Tower and Small Form Factor) (DDR2-6400 - Non-ECC) Desktop Memory at Amazon.com
Used Dell OptiPlex 755 Tower Desktop PC with Intel Core 2 Duo Processor, 8GB Memory, 500GB Hard Drive and Windows 7 Pro (Monitor Not Included) - Walmart.com
Dell OptiPlex 755 Desktop Complete Computer Package-4GB Memory Windows 7 Home Premium | Wiz Electronics Inc
Dell Optiplex 755 Motherboard | Laptech The IT Store.
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
4GB 2x2GB RAM for the Dell OptiPlex 755 Ultra SFF RAM Memory DDR2 | eBay