How to add gray fields in a form in word 2007 and lock the form?

With IE browser open click tools\internet options\then
click the colors button at the bottom left of the general
tab and then you should have a check mark in the "use
windows" box or you can choose the text and background
colours you want. Keep smiling.

First go to Office button > Word Options > Popular and check the option for
"Show Developer tab in the ribbon".

Now select the Developer tab. In the Control section, click the button that
looks like a folder, and that shows the tooltip "Legacy Tools". The Forms
fields are the first row of the dropdown on that button.

The Protect Document button is further to the right on the Developer ribbon, and
also at the right end of the Review ribbon.

The lock button that was on the Forms toolbar in 2003 isn't visible by default,
but you can add it to the Quick Access Toolbar by right-clicking the toolbar,
choosing Customize, setting the category to Commands Not in the Ribbon, and
selecting the Protect Document item to add.

Try selecting the whole document and pressing ctrl+shirt+F9, it will unlink all fields.