Originally Posted by worshipme
It doesn't really matter whether you put it on before or after, although I always do it first. You have to use the one that came with you motherboard.
Please explain how your would put it on after...
Yes, you must put it on before you install the motherboard. It goes in through the inside of the case through the I/O shield hole, then the motherboard goes in behind it. It should be held in pace by the case.
Your motherboard must not be quite in the case right if you can't put the video card in. To clear it up for certain, do the slot and connector on the motherboard and graphics card fit together? Or is it just not fitting on the case right?
Also, you might as well take the mobo back out and wait to put it back in until after installing the processor. If you install the processor and heatsink while it's in the case it makes the task rather hard, especially if it's a big heatsink.