Dimension 4700 Upgrade

I have a Dimesion 4700 that has a PCIe slot.  Previously I had been using the onboard video but wanted to upgrade to a better video card.  I purchased a refurbished "Dell ATI Radeon 2400 HD Pro 256mb PCIe Video Card HW916" on Ebay. 

http://cgi.ebay.com/Dell-ATI-Radeon-2400-HD-Pro-256mb-PCIe-Video-Card-HW916_W0QQitemZ380114615713QQcmdZViewItemQQptZPCC_Video_TV_Cards?hash=item588098bda1&_trksid=p3286.c0.m14&_trkparms=65%3A12%7C66%3A2%7C39%3A1%7C72%3A1234%7C240%3A1318%7C301%3A1%7C293%3A1%7C294%3A50

I thought that this would work with my flat screen monitor using the included DVI Y splitter but when I plugged it in I didn't get any video.

Am I doing something wrong?

Randy