DDR and DDR2 as a main memory

You are going to have to be a little more descriptive of "it doesn't work". What error messages are you getting, what are you trying exactly, does something hang or error out or get a warning? Where are your reset and exception vectors pointed to? Are you using the bottom few address spaces in the ddr? I have a faint memory that you are not suppose to use them as they get changed with calibration or something, but can't think of where i remember that from. Does you system come out of reset? Do you have valid clocks everywhere they are used? Does the DDR pass calibration? Have these boards been tested or worked with other designs, just not with your current design? Have you tried to run a simple hello world program running from ddr? Have you tried to run a simple hello world program with a nios system not connected to ddr just to verify you have working knowlege of the nios ide and that your board generally works?