Built new computer, monitor has no signal

I just built my first system. The fans and CD-ROM drive turn on, but my monitor display just says "no signal." I tried the monitor on my laptop, and it works fine there.

The video card is a 9800 gtx+, and the CPU is an E8400 core 2 duo processor. The power supply is a 450W corsair model (http://www.newegg.com/Product/Product.aspx?Item=N82E16817139003). The video card has VI connections, and I used an adapter to connect with my monitor's VGA interface.

I'm not sure which is more likely the problem: Did I install the video card incorrectly? Or did I not get a PSU with enough power?

on my firrst build it worked until i pulled the RAM out to show a friend how small it was and i didnt put it back corectly and so when i powered on it appeared to work because the fans were spinning and i got no sygnal, i thought the GPU was dead. almost send the Board back to new egg. lololo