First of all a registry sweep , or any other sweep for that matter , ain't gonna solve this problem.
Quote: Having found "hundreds of errors" in my Registry, I then found RegSweep was not a freebie
Now there's a surprise Although you'll likely have a few registry errors , we all do , you'll find this is a marketing ploy to get you to buy the product.
Net framework problems such as your's are very common , in fact we had a similar one to yours on the forum the other day ,which was successfully solved. There's never a guarantee however so before i suggest the same fix ( it means a bit of uninstalling ) could you check the error code please. Don't know how you got the error code , but if you could double check by going to windows updates........open Internet Explorer click on tools > windows updates. In the left hand pane click on "review your update history" and look for the failed update in the list. Click on the red cross and a screen will appear with an error code. ( apologies if you've already done but need to be sure ).