Instant Rails when Apache and mySQL already installed

Any tips on how to deal with Instant Rails when you already have Apache and mySQL installed on your computer (running Windows XP)? The main Instant Rails window says ports 80 & 3306 are already being used by Apache and mySQL. Is there a way to point Instant Rails toward my existing Apache and mySQL installations?

Also, when I run “gem update --system” (per page 19 of “Simply Rails 2”) I get
ERROR: While executing gem . . . (Gem::RemoteSourceException)
HTTP Response 302 fetching http://gems.rubyforge.org/yaml