I've found on this page:
http://made-of-stone.blogspot.com/2005/12/setting-up-iis-for-rails.html

There, he told to make a change in the request.rb on C:\MyApp\vendor\actionpack-version\lib\action_controller\request.rb

He said to change "request_uri" method to be like:

# Returns the request URI correctly, taking into account the idiosyncracies
# of the various servers.
def request_uri
if uri = env['REQUEST_URI']
(%r{^\w+\://[^/]+(/.*|$)$} =~ uri) ? $1 : uri # Remove domain, which webrick puts into the request_uri.
else # REQUEST_URI is blank under IIS - get this from PATH_INFO and SCRIPT_NAME
script_filename = env['SCRIPT_NAME'].to_s#.match(%r{[^/]+$})
uri = env['PATH_INFO']
uri = uri.sub("#{script_filename}", "") unless script_filename.nil?
uri << env['QUERY_STRING'] unless env['QUERY_STRING'].nil?
uri
end
end


And the problem is over, i got my app running!

Ps: But still there is another question: my older apps does not work good now... Running on webrick and mysql database, they can't connect to mysql, it responds:

NameError in Post#index

uninitialized constant Mysql
...
...
...
This error occured while loading the following files:
mysql.rb
...
...

-------

And an alert pops up, saying that could not found LIBMYSQL.dll ... I believe RubyForIIS.exe change some configuration on c:\ruby about MySQL, am i right?

Cool! I'll try to update the documentation. Which windows platform are you on?

The installer does place a MySQL dll. It might be that this is in a wrong location for your setup.