Something similar to this happened to me not too long ago. My current setup seemed to be tearing up PSU's left and right, I had to replace the PSU three times in a span of a couple months to figure out what was going on, I will give you my story in hopes that it will help you. The first time it happened, my computer would shut down randomly, just completely turn off, I didn't realize this was a result of a failing PSU. The first time it turned out that with the failing PSU, it took my Video Card down with it, so I had to replace both and all was fine, this was a 600W replaced with a new 600W generic PSU. Of course as luck would have it, the same thing happened again, this time, I was fortunate enough to not loose any of my other components, just the PSU. I finally got fed up after it happening again, so I replaced it with a bit higher quality 680W PSU, I have never had a problem since.
What I'm thinking is that something may be sucking a large amount of power from your PSU and burning it out, you might have lost your Video Card along with it, as you hear a one beep, and the fans are running, which means everything else should be ok. I would suggest you find another computer with the same Video Card slot and test it in that, if that computer doesn't start up, then it is most likely your video card that may be stopping you from booting.
