I attempted to download a coupon to save a few dollars and now my computer is locked up. Box says..."your computer can't be shut down now because software is being installed. Keynote is being installed. Interrupting the install may damage your computer. you can shut down when install is complete." This is a half hour later.
Don't worry about damaging your computer. OS X (and Windows now) can't be damaged if you shut down in the middle of software installation. OS installation maybe, but not software.
Go ahead and hit that power button.
If you try to print a webpage and it starts to install software, then it may be a piece of malware.
Try taking a screen shot and print that out.
Here are some sample commands to get a capture of your screen:
- Command+Shift+3: takes a screenshot of the full screen or screens if multiple monitors), and save it as a file to the desktop
- Command+Shift+4: brings up a selection box so you can specify an area to take a screenshot of, then save it as a file to the desktop
- Command+Shift+4, then spacebar, then click a window: takes a screenshot of a window only and saves it as a file to the desktop
- Command+Control+Shift+3: take a screenshot of the entire screen (screens if multiple monitors), and saves it to the clipboard for pasting elsewhere
- Command+Control+Shift+4, then select an area: takes a screenshot of selection and saves it to the clipboard for pasting elsewhere
- Command+Control+Shift+4, then space, then click a window: takes a screenshot of a window and saves it to the clipboard for pasting
I would suggest using the first one (Command-Shift-3), taking a capture of the webpage with the coupon, opening that file that gets created (located on your desktop) and then printing that.