OK, Andi:
I think I found it.
The XP setup file in this driver has the hardware ID in it, which means that the driver is good for more than just W7 x64 but you may not be able to actually run the exe using XP. But there is an XP 32 bit driver folder within this file.
%ST.DeviceDesc%=STHDA,HDAUDIO\FUNC_01&VEN_111D&DEV_76D9&SUBSYS_103C188F
After you install the chipset, graphics and msuaa driver, rebooting after each installation try this>
Download but do not run this driver...
Then download and install this free file utility.
After you install 7-Zip, right click on the IDT audio driver you downloaded and select the 7-Zip option from the menu.
Select 7-Zip to Extract to: and I let it extract the exe to the name of the file so it is easy to find in the next step.
OK...here is where the hard part is...you are going to have to find what device in XP has that IDT hardware ID you posted, because I think that is the only way you are going to be able to install the driver.
When you find it, click on it and then click on the driver tab. Click on update driver and select the manual search and then select the Have Disk method of installation.
Browse to the driver folder that 7-zip created\WDM\WinXP\STHDA, and select the IDT High Definition Audio CODEC from the list and see if the driver installs that way.