Windows 7 Dual Monitor Configuration? HELP!?

I am trying to set up dual monitors on my Dell Optiplex GX620 running Windows 7 32-bit. I bought and installed a new graphics card, an ASUS EAH5450 Silent PCI-E LP 512MB DDR2, with a DVI to VGA connector and a VGA Splitter. At first I used the splitter but only got two of the same screen on both monitors. Now I've put the DVI to VGA connector in the port for the first monitor and the second monitor in the VGA port and only the first monitor shows up, but the second one stays blank. It doesn't come up with a "no signal" message though, so to test it out I put a file on the desktop and dragged it over to where the second monitor should be and it has disappeared and stayed on that side, so the scond monitor must be detectable but it just isn't coming up. I've gone into the control panel menu and the second monitor is detected, I try to "extend" but nothing happens. What am I doing wrong? Do I have all the correct gear for this setup or am I missing something? I've read in places that the GX620 doesn't support dual monitors but I've read elsewhere that it does with correct configuration.