Will post this duplicate reply in this thread as well, in case someone does a search on the forums for the same issue in the future.
Problem solved!!!!
After further digging around on the web, it transpires that this driver regularly fails to install along with the Intel Chipset drivers during a reformat/clean install. Quite why it does this I have no idea.
So what you need to do is go to Device Manager, click on the SM Bus Controller and then click on "Update Driver".
Then point Windows towards the root directory of the chipset drivers where all the
.inf files are located.
It will then pick up the SM Bus Controller from there and install it correctly.