You will need to replace your PSU with a more powerful one that has the required connector. Although you can get by with only 450W, in your place I'd probably choose at least 500W, and definitely a quality brand. This list is dated, but will give you a place to start: http://www.tomswiki.com/page/Tiered+PSU+Listings?t=anon. Choose one from tier-3 or better.
See the black plug thats plugged into your dvd rom drive..... ?......... those are the kinds of plugs that plug into it. Try and find 2..... I see 1 just hanging there. there may be one hidden. You may get away with using just 1 I don't know.