First. Your windows IS running, your whole OS IS accessible and nothing is lost. I know people who use their computer with just the !Run -dialog. :)

So.
You can always use the taskmanager to run your browser and regedit. Then the 'net is full of documents on what to do in order to restore Explorer as the shell. For example this forum contains multiple instances of links to them.

Read the IMPORTANT -topic on the top of this forum and restore the lines mentioned there (more specifically, just the shell -line).