If the computer is wiggling in my truck it is because i am off roading...
My board is a heavy duty board and is designed to be in a harsh environment with built in video and audio. Heck the only things I added to the board were the memory and CPU. The Hard drive has a locking SATA cable on it and in the case it is crammed up against the side of the case and won't move. But not so hard as to break off the wire.
A standard PCI card has no hold down for it and it is easy to vibrate loose. I am also with you here that you are better off getting a USB sound card than to use a PCI card. If you don't have a built in card then you will want a USB card. Hopefully your video card is built on board. If it is not on board hopefully the slot you put it in has a locking mech to keep the card in place.
The memory is clipped in place in most computers so it just depends on what kind of system it is locked in place with. If it is laptop style memory it is locked down pretty well.