KB ID 0000640
I installed a classroom full of PC’s today, after setting them all updating, and rebooting, I went to lunch, and came back to find them all displaying this,
Stage 3 of 3 Preparing to configure Windows. Don't turn off your computer.
I went and did another room, came back, and there was no change.
It turns out this is a known problem if you are installing KB2533552, to get round the problem simply press CTRL+ALT+DELETE, and you will be presented with the login page.
Microsoft recommend you install the above update separately.
Note: It will affect both Windows 7 and Server 2008 R2.
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