Internet Explorer 10 does not appear on the list of supported browsers, so it may not be possible to get it to work with IE10.
From [the WatiN home page]
Works with Internet Explorer 6, 7, 8, 9 and FireFox 2 and 3
Link Removed - Domain hijacked by Spammers See https://web.archive.org/web/20161230004014/http://watin.org/ for old versions of the site)