Open up F2.1i, and perform the synthesis there as a Virtex device.
Then, open up FPGA Express stand-alone and open the DPMCOMP.TMP.exp file in your project directory. In the Design Sources frame on the left of the screen, highlight the top level/main project file and then click the "Create Implementation" button. Select the same Virtex device in the Setup box, and click "OK".
Once implementation is finished, exit FPGA Express and open Design Manager stand-alone.
Highlight the project and the click the black arrow button at the top left. Now, in the setup box, select the Spartan-II device that you want to target and click "OK".