From the best I can tell you should be able to uninstall the High Definition audio driver package KB888111 package through add/remove programs without any problems.
Microsoft has an article about it here: http://support.microsoft.com/kb/888111/en-us
They don't give a lot of information about uninstalling but did say if you uninstalled it and then reinstalled it would not show in the add/remove programs.
I would create a restore point before you uninstall it though just in case.
1. Click Start, All Programs, Accessories, then System Tools.
2. Click System Restore to launch the System Restore wizard.
3. Select the box next the text labeled "Create a restore point" and click the Next button.
4. Type a description for your new restore point. Something like "Before I installed some program that may cause my system major grief" would do just fine, but you don't have to be that descriptive.
5. Click Create.
I don't know if you can stop it from loading at startup it my be a service, you can try though.
Start > Run > type msconfig > click OK > Startup tab.