If you have 7040 MT, this video shows how easy it is to open the side panel. go to play time 2:34.  Unboxing and disassembly Dell Optiplex 7040 MT PC - YouTube [IMAGE] if you have 7040 SFF, this video shows similar way to open side panel.  Dell Optiplex 7040 small form factor teardown and system overview - YouTube
Hi, i tried to open my optiplex 7040 case, but when put the blue fuse [or whatever it is] down, it wont open  
cant open my optiplex 7040 case