This is dated now, as it’s only for Windows XP – however it is left here for historical purposes.
I experienced tremendous problems installing these drivers under WinXP SP2.
The following steps worked for me.
1) Install windows XP.
2) Download and install KB888111 from here http://www-307.ibm.com/pc/support/site.wss/MIGR-68974.html
If this link doesn’t work – search for KB888111 – install this patch.
3) Download and install “Common Windows update modules (United States only)” (ignore the US only) from here;
4) Install the latest version of Microsoft DirectX.
5) Reboot the laptop.
6) Any attempts to install the sound driver at this stage will still result in the error message “The HDA Audio bus driver is required and not found.” and will terminate the installation process immediately.
7) At this stage, look in Hardware / Device Manager, and you will most likely see a yellow question mark against a “PCI Device”.
8) Uninstall this device and reboot.
9) You should now be able to install the sound driver successfully.