If you wait a little, the uninstall should finish.
if you wish, you can rename the users configuration folder to do a quicker uninstall.
see this page for details on locating the configuration folder:
http://www.webassist.com/tutorials/Common-installation-issues
rename it, then start DW to recreate it. after it is recreated, open the extension manager, and uninstall all extensions, then reinstall them.