I just upgraded my older system (1.4 AMD Tbird) with a BFG GeForce 6800 128mb. I wanted a boost in 3d games, and thought the vcard was the only really necessary upgrade. Unfortunately though, I've had some dissapointing results. I was hoping to be able to play Rome Total War with max settings, but my comp still can't do it. I can't even play the nvidia 6800 demos! They stutter along at an aburdly low frame rate. I'm guessing;
A: My slow CPU isn't supplying enough information to the fast 6800, and I need to upgrade my CPU.
B: This version of the card is crippled by having only 128mb, and the 6800 needs 256mb to take advantage of it's full potential
MOBO - ASUS A7M266
CPU - AMD Athlon 1.4 266
RAM - 512 PC2100
VCARD - BFG GeForce 6800 (overclocked) 128mb
I don't think a TBird 1.4 on any mobo will make it much better without OC'in, but that is a AMD761 mobo, so it is not a speedy DDR Socket A board. But at least you aren't on a KT133a running PC133 memory, which would be much worse. Anyway, you are most likely totally cpu/system limited in the game you are trying to play.
Many games you should see higher settings being playable than if you upgraded from a older video card. But in other games you will be completely CPU/system limited, and the 6800 can't help in those cases. That is a decent video card, all you need is a new mobo/cpu/ram to take advantage of it.
If that kind of a full upgrade is too costly for you now, you could look <A HREF="http://www.asus.com.tw/support/cpusupport/cpusupport.as..." target="_new">here</A> and you'll see the cpu support list for that mobo. It maxes out at a XP2100+. If you can find a <b>Palomino</b> Xp2000+ or 2100+, it will definately help some. Just make sure you have/or flash to a bios version that supports it before pulling the TBird 1.4GHz. If you were to buy a used cpu and after installing/testing it sell your 1.4GHz again, you may just end up with a very cheap upgrade.
Looking at <A HREF="http://www6.tomshardware.com/cpu/20030217/cpu_charts-24..." target="_new">THG 65 cpu shootout</A>, you can get an idea just what the cpu/system does to gaming performance. All tests were with the Radeon 9700 Pro, which was the best card of the time, but is slower than yours. Shows you just how crippling a slow system can be doesn't it. Anyway, since your mobo/ram is DDR and would remain the same, look at the XP1500+(with DDR) as apposed to the TBird 1.4C(on SDR) for a reference to your system. Then you can see what a XP2100+ does with the same card. Now in this case, both are playable, so the 20% boost in framerates in UT2003 wouldn't be a good reason to upgrade. But in other games it just may make a difference between playable and sub-par cpu bound play.
MSI K8N Neo2 platinum, A64 3000+, 1GB Corsair XMS 4000 Pro Series, Radeon 9800 Pro