I solved this problem completely later that day.
From the Emachines site I downloaded and installed the file:
This dirver is for vista but it must also be for XP because it really worked well.
This can be found at www.emachines.com
click on: customer care > product support and downloads.
Then select desktops, T-Series, and T5230.
By clicking the plus sign [+] next to downloads below you will see a list of drivers including:
Realtek High Definition Audio Driver
be sure to click on the
Download (36.29 MB)
and not just the readme file.
download this to your computer and run the self extracting install.
Then right click on the MyComputer icon (on your desktop or windows explorer) and choose Hardware tab and Device Manager to verify that the RealTek audio device is working properly.
You'll see the other broken devices there of course.
I went to www.nvidia.com
nvidia is easy to navigate. Just click on Download Drivers
The GeForce 6150SE video card driver
From Option 1 select GeForce, GeForce 6 Series, Windows XP and click the Search button. Then click download now. to save the file to your computer so you can click on it there to perform the driver install. This made a huge difference in the quality of my display.
nForce 430 chipset driver installers
From Option 1 select nForce, nForce 4 Series, GeForce 6150SE/nForce 430, driver, windows XP. Then click search followed by Download Now to save the file to your computer for installation.
This took care of everything but the generic PCI device.
For that, I hooked my legitimate copy of Windows XP to the internet using my newly functional RJ-45 network jack and an ethernet cable and let windows find the driver for me. Which it did seemlessly. No More Yellow questionmarks in the Device Manager!
That was mostly painless.
I noticed that some quicktime programs didn't like my nVidia driver so I created an alternate hardware profile to use the generic windows video driver and that solved that problem too.
I didn't have to open the case on the emachine and I still have the Vista install disk that came with it if I want to go back.
I'm impressed that my games work fine on XP home when the didn't on Vista. I expected it to be the other way arround.