Whether your scores are good depends on your settings. What is your FSB and multiplier? If you are running the CPU @ 100 MHz FSB (12x100) then you can do quite a bit to increase your 3DMark scores.
If you have a 1.2 GHz T-Bird, you have to determine if it came 'unlocked' from the factory or if you have to unlock it using the 'pencil trick' which you can read about on the AMD CPU forum or somewhere else around here.
Even if you don't 'increase' your total CPU speed, you can see significant performance gains. Configuring your CPU to run at 9x133 (1.2 GHz) will give you significant performance gains over running at 12x100 (1.2 GHz). With PC150 RAM you should be able to up the FSB to at least 140. After that you may run into problems possibly with other peripherals.
You can also of course overclock your GeForce. Go to tweakfiles or an NVidia website for a video card overclocking program. I have heard many reports of 3DMark score increases of 400 or 500 points from overclocking the video card.
You can also find KT7 bios optimization guides. They are not exactly the same as the KT7A bios but most are the same and optimizing those settings can significantly improve performance.
Your drivers are going to offer about as much performance as you can get from the card. There is not a significant difference in speed between 6.xx drivers and 7.xx drivers and some people have had problems with 7.xx drivers so you should be fine there.
I would say that if you have not optimized the bios, if you are running at 100 MHz FSB and can increase it to 133 MHz FSB +, and if you can somewhat overclock your GeForce you should be at 10,000 3DMarks. If you have already done the above then you may have hit your plateau.
