Nothing special about running Windows setup again. It's no beeg deal and can fix lots of stuff without messin' with your settings too much. Apart from the desktop and virtual memory just about everything will be the same.
But, for the record, removing DX is not such a beeg deal either. Simply extract the version you installed. Generate a file list and make that into a batch file to delete all those files. Delete all the DX entries in the registry and run the batch file from DOS. After rebooting run RegClean or better yet a third party cleaner like Registry Cleaner in Fix-It Utilites. Reinstall the DX version of your choice.