Hi,
Welcome to the forum.
You should never downgrade unless you check first. I hope you backed up your Vista OS.
I'll give it a try.
We will have to find these drivers separately.
Here is the spec sheet of your model:
http://h10025.www1.hp.com/ewfrf/wc/d...454923&lang=en
You will need this to Identify the types of drivers you may need.
This is the first driver you should install (Chipset 945G):
http://downloadcenter.intel.com/Prod...=2115&lang=eng
Then be sure to do a full Microsoft update
Sound card Realtek High definition Audio:
http://www.realtek.com.tw/downloads/...Audio%20Codecs
Graphics Card nvidia 8400GS:
http://www.nvidia.com/object/winxp_169.21_whql.html
You may or may not need these. XP may have found some.
When done installing these, go to the device manager and post any errors (highlited in yellow or red exclamation points.
Thanks,
Bill