simple captcha instllation problems

I am running XP. Downloaded simple captcha from expressica, unzipped into vendor/plugin. Ran

rake simple_captcha:setup.

Gives me error: rake aborted! don't know how to build task 'simple captcha:setup_old' I checked rails version by

gem list rails

Gives me rails <2.3.5, 1,2,2> can someone tell me how to fix this?