My Win7 machine takes a few minutes per single update file. To install 20 or 25 updates it can be half an hour or more.
Did you watch the update window as it installed update files one by one? Did it say 'Done' 19 times, then get hung up on #20?
Or, is the message window in the background? Close/hide extraneous windows. Press Alt-Tab several times to cycle through all the programs/windows you have open.
At least a couple times I saw one update file failed, and it printed a notification, then went to the next update file.
If your machine remains stuck, I think it is okay to press the power button to shut off the computer. Next time you start up, the system log will tell the computer it did not successfully install the remaining updates. It will notify you sooner or later that the updates are available. You might have luck next time.
If the computer refuses to start up in normal mode, then start up in Safe mode. You may need to do some diagnostics, examine the Events list, run an anti-malware program, etc.