So, I bought and installed New Vegas (DVD version) onto my computer, but it instantly decided to link it to my steam account, so I guess the two are inexplicably tied now.

However, the problem is this: The audio and video are either lag behind, or are just not there period. In fact, to make the noises go off and make things load, I have to hit esc to go the menu, and then reenter, and then stuff magically works. I had to keep "refreshing" the game just to get through the character creation phase.

What can I do to fix this? I can run the graphics perfectly fine; I could run oblivion fine, and even on high settings everything moved and worked fluidly; sometimes things just wouldnt load.

Too frustrated and incompetent to troubleshoot myself, can someone please help me?

Fallout 3 nv uses steam so yes your copy is linked to your steam account. This is normal.

Make sure your graphics and sound card drivers are up-to-date. Do the same for your motherboard drivers too.
Be sure your runing the updates with the right credentials. Right click and run "as admin" is what i usually do when in doubt.

You can also try a clean boot to windows.
clean boot link:
http://support.microsoft.com/kb/929135

Make sure your run-times are up-to-date
vc2008 run-time sp1:
http://www.microsoft.com/downloads/en/details.aspx?familyid=A5C84275-3B97-4AB7-A40D-3802B2AF5FC2&displaylang=en