Power off, Power back on. As soon as you see the Gateway logo, start pressing the F8 keep repeatedly. This should bring up the Advance Boot menu. If you miss it, power off and try again. At the menu, choose "Last known good configuration." and it should revert back to before the update started.
Once you are back into Windows, do the following:
1) Open a command prompt with admin privileges and type SFC /SCANNOW <enter> This will run the System File Checker which will verify that all of your Windows files are present, intact and undamaged.
2) At the command prompt type CHKDSK /f <enter> - you will get a message that the drive is locked and should it perform the check the next time it reboots. Say Yes
3) Exit the command prompt and restart the machine.
4) Back in Windows, attemp to run the update again.