Sound is terrible on win XP and its ok on my other win 7 pc

Find the individal components make and model in device manager and go get the drivers from them.

This is another tough one.
Since GW does not have Win XP drivers available for your system, it will be difficult to find a sound driver that will work. You could try to use the Vista driver, but I would be skeptical that it will work to use that driver because of the way that sounds are processed in Vista/Win 7.
You didn't mention why you did the downgrade, but if it was performance related, Win 7 should work fine with your system. If there was a certain program etc., that you need, there is another option.
There are many USB soundcards that will will work well with Win XP, and they should not have the XP problem since their hardware is designed to work with XP. Note: If you go this route, make sure you choose one that is Win XP compatible. One other thing on this option, though. Your internal speakers may not route sound through the USB soundcard, which would mean then that you would need external speakers to get sound. I understand that may be a deal-breaker, which is why I would (unless you specifically need XP) either go back to Vista or upgrade to Win 7. Some version of Win 7 feature "XP mode" which allows you to run programs in a virtual Win XP environment. I have not had perfect luck getting XP programs to work, but it's worth a try.

Try here:-

http://www.sharedownlinks.com/creative+sound+blaster+ct4870+driver+for+windows+7+32bits.html

hello sir my pc pent 4 win 7 & sound card not work crectly

Hello

Win 7 does not support direct sound.Go to controlpanel and run the windows update.
This should find your sound device and download the drivers for it.

Check the pc manufactures websight for audio drivers also for win 7.

Ok try formatting the usb drive under XP, put a small file on it, say a pic or something, then take it to win 7 & see if win 7 is OK with it, if OK, well then copy files and take back to XP.. ya should be able to "see" ya files now.

Check the Sony website for any and all available windows 7 drivers for your machine. Start with the chipset drivers, then video, sounf etc. Sound will be crappy if you don't install the chipset drivers first.