Your father-in-law has an international keyboard layout enabled. With this layout, the " key becomes a "setup key" or "dead key" for typing vowels with an umlaut or diaeresis. As you have noted, in order to type quotes, it is necessary to press the quote key twice. Here's how to fix the problem:
- Click the Start button and choose Control Panel.
- In the Control Panel, select Region and Language.
- Select the Keyboards and Languages tab.
- Click Change Keyboards...
- Ordinarily the language selected (since it is the default) would be "English (United States) - US," but you will probably see "English (United States) - United States-International."
- Click the arrow beside the selection to see whether the default US is available. If so, select it and OK out of all the dialogs.
- If not, click Add, scroll down to English (United States), check the appropriate box, and click OK.
- If you're using "English (United Kingdom)" and click "Show More...," you'll find a plethora of different keyboards, but the only international one appears to be the "United States-International" one. In any case, you would want to instead select the box for "United Kingdom."
- When you've got the keyboard set to the appropriate US or UK one, OK twice to exit the dialog.