Ran into this issue today when doing a SharePoint 2010 install from media on several new Windows 2008 R2 SP1 machines.

“There was an error during installation. The tool was unable to install Hotfix for Microsoft Windows (KB976462)”

Kicked off he Pre-requisite installer and got that error after it finished. Scratched my head because it didn’t really give me a good clear concise reason why it failed. I figured maybe the download had gotten hung possible due to a network issue and re-ran the pre-req installer. Of course this time all was good. No biggie. Then I moved to my other machines where I’d kicked off the pre-req installer at the same time on each, and sure enough that all had the exact same error.

Did some quick digging and sure enough, looks like Windows 2008 R2 SP1 already has fixes in the KB in it. So microsoft recommends, (wait for it…) Run the pre-req again. 🙂

Kicked off the pre-req again on the other boxes and all went through good.

Microsoft support KB here. http://support.microsoft.com/kb/2581903