New video card problems

About a month ago, I bought a GF2 GTS w/ 32M DDR ram(AGP) to replace my Voodoo3 3000 (PCI).  Sence I got it, I can not see any improvement in 3D based games.  However, I do see a  speed increase things that don't require 3D hardware(mainly arcade emulations.)
The only game I realy compaired the cards in was Unreal Tournment.  My voodoo seemed very smooth, but would lock up when displaying complex graphics, where as the GF2 just is very jerky all the time.  What could cause this?  I downloaded Detonator, but the performace droped even more.  I tweaked the bios, but never saw a true improvement, so what could cause this?

Oh, another small problem I had, when I first installed it, I kept getting the no video beep.  I removed the card, and re-installed it, and it worked.  Today, after installing a new fan, I cut my computer one with just power connected to see if the fan was right.  After I saw everything was fine, I put it together, and cut it on...I got the no video beep.  After messing with the cable for a while, I opened my computer up  and reseted the card, and it worked fine.  What could cause this?