The Windows installer has option [x] Show Readme that is checked by default. It results in file "C:\Program Files\Apache Software Foundation\Tomcat 6.0\webapps\ROOT\RELEASE-NOTES.txt" being opened in Notepad. In TC 6.0.18 and in current RC for 6.0.20 that file has LF line ends. Notepad cannot properly display such files.
Created attachment 23716 [details] Screenshot
Fixed in trunk and proposed for 6.0.x
This has been fixed in 6.0.x and will be included in 6.0.21 onwards.