I am reluctant to advise that you format and reinstall as you are so close to getting this sorted and you may well end up with the same sound card driver problem.
What do you think Tyger?
Am I right in thinking that you have never successfully uninstalled the sound card driver?
If you go to Device Manager and highlight it - do you not have the option to delete?
If you do and it will not delete - try it in safe mode (tapping f8 > safe Mode) We need to uninstall the old driver then install the new downloaded one.