8GB 4X2GB Dell OptiPlex 755 Series Desktop/PC DDR2 PC2-5300 RAM Memory at Amazon.com
Dell OptiPlex 3010 Desktop Computer PC, 3.20 GHz Intel i5 Quad Core Gen 3, 16GB DDR3 RAM, 240SSD SATA Hard Drive, Windows 11 Professional 64bit with 22" LCD Monitor - Used - Like New - Walmart.com
How To: Dell Optiplex 755 Ram Upgrade - YouTube
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
Dell OptiPlex 755 SFF PC Intel Core 2 Duo 2GB DDR2 160GB DVD - XP Ready - NO OS | eBay
Refurbished: Dell Optiplex 755 Small Form Factor Desktop (R2/Ready for Reuse) with Intel Celeron 430@1.80GHz, 2GB RAM, 80GB HD and licensed Windows 7 Home Premium from a Microsoft Authorized Refurbisher - Newegg.com