I am new at replacing computer accessories. I just purchased a ASUS AMD Sabertooth 990FX motherboard and I am about to place it in my HP case. Do I need to put the videocard in first or do I put it in after I secure the motherboard into the case? This motherboard should fit in my case correct? it is a full size CPU case from HP. Thank you.
http://www.youtube.com/watch?v=wZPXSy3saKY. Here's one video with some pointers. I recommend you test the board before mounting it. You'll need to install the ram and cpu/heatsink first anyway before mounting it, so leave the power supply out if possible so the connectors will reach the board.
Take a look at the following guide http://www.tomshardware.com/forum/261145-31-perform-steps-posting-post-boot-video-problems
Pay special attention to the section describing how to breadboard your system before installing it into the case.
You won't be able to install the video card before installing the motherboard. It is designed to be inserted after the motherboard is already installed.
Even though the above listed guide is designed to help you find "Won't boot/no video" problems, it can also be used to help you successfully build your system. Just follow through all of the steps and you will greatly increase your chances of getting it right the first time.
Also, I would suggest that you test fit the motherboard in your case and make sure that it fits before you actually install anything onto the motherboard. If your case is in fact designed to hold an ATX sized motherboard you may still need to move or install standoffs to get it installed correctly. Make very certain that you DON'T have any standoffs in a position that doesn't match up with the mounting holes in the motherboard. You dont want to end up with a short.
After you have made sure that the board will fit correctly, remove the Motherboard from the case and then go ahead and install the memory DIMM's, the CPU and the CPU Heatsink assembly. Then you can reinstall the motherboard into the case. Continue building the system by installing the Video card(s), HDD(s), other devices and running all of the cables. It is also a good idea to tie your cables down and bundle them together wherever possible to create a cleaner look and help improve air flow. Take your time while running the cables so that you can plan how to tie them down without stressing them.