I upgraded my 4year old Dell Costco from 7Pro to 10 Pro and the install went smooth. However, I soon discovered that boot up time was much longer than 7. I saw the Windows logo then it sat for almost 2 minutes with a black screen until the login came up. Then twice I tried to restart the laptop, once the screen went blank but the computer stayed on. Other time it just sat there saying restarting, so I forced shut down. I used the feature to roll back to 7, but then it tried to start up, and I got a blue screen. Even the startup repair failed. I had an image of W7 but decided to do a clean install with the Dell media. Strangely KB3035583 is not in the updates. BTW, for anyone reinstalling W7, there are about 200 updates at 830mb from SP1 install.