Added new power supply, video card, and monitor.... now computer won't start. Why?

I'm a fairly experienced computer tech, but can't figure this out. I swapped out my old Velocity Micro power supply (it's a VM computer) for a newer model which has the power capabilities needed for a PCI-E video card with PCI-E 6-pin power requirements. At the same time I also installed a PCI-E video card with two 6-pin power connectors and a new HDTV which I'm using as a monitor.

While installing the new power supply, I had to take apart a good portion of the computer, but was careful to get everything back how it looked before. Tested it out after installing the power supply and video card and while all the electrical innards seem to function correctly (fans, lights, etc), I'm not even getting a signal on the new monitor. I tried all 4 DVI ports (between the two cards) and nothing. Then trying to isolate the problem, took out the new card, put the old card back where it was, and no change. That being said, I don't think it's the new video card. Any thoughts on what's going on here? For the record, I was careful about ESD, so while I did do a lot of messing around, I doubt it's that.

Thank you!Added new power supply, video card, and monitor.... now computer won%26039;t start. Why?
Is it plugged in?Added new power supply, video card, and monitor.... now computer won%26039;t start. Why?
Try using a basic monitor to see if that works first. You might have installed something incorrectly or pulled something out of place while messing inIde. Also hdtvs and hd monitors are really hard on your system so be careful with thatAdded new power supply, video card, and monitor.... now computer won%26039;t start. Why?
First thing you need to determine is,

When you first power on the computer, do you get any beeps from the motherboard?



If no beeps, the most likely problem is a bad power supply. New power supplies can be DOA. Don't let LED lights and spinning fans fool you into thinking your power supply is good. A bad power supply rarely fails to a %26quot;do nothing%26quot; mode. Most bad power supplies will still light LEDs and spin fans.



If you DO get beeps (or even a single beep) from your motherboard when you turn the computer on, you need to concentrate on your monitor. Are you using an adapter between the video card and the monitor, such as a DVI-HDMI adapter? That could be part of the problem.



I'd simplify a bit. Put the old power supply and video card back in. See if you can get the computer to boot. If you can, then try the new monitor on the old video card. If that works, swap in the new power supply. If that works, swap in the new video card. Eventually, you'll find a combination that doesn't work with all components known good EXCEPT ONE. Then at least you'll have a better idea of where the problem might be.Added new power supply, video card, and monitor.... now computer won%26039;t start. Why?
check your work ? power switch ? drivers ? anything come with a install disk.