If you are stuck on this step of the installation process for TracerPlus Desktop or Tracerplus Connect, first exit the installer. Once the installer has been fully closed out, re-start the installation process. When given the option to select what software to install, make sure to un-check the Windows Mobile Device Center option. The installer should complete now without issues.
Once the installer has finished, you will need to install the Windows Mobile Device center from its stand-alone installer found here: http://support.microsoft.com/en-us/kb/931937
Make sure to install the correct version for your PC (32bit or 64bit).