Even if you know you're right, if Microsoft Word gives you a squiggly line of any kind, it unnerves you and makes you paranoid that you're turning illiterate, amirite?

I used the word its in a sentence and it gave me a purple squiggly so I changed it to what it suggested and it gave me a green squiggly so I changed it back and it gave me purple again and so on in this infinite loop...I was right the first time, but it was still annoying to see the dumb line

For 07...
Menu > Word Options > Proofing > Go down a bit > Uncheck the boxes that say check for grammar or something. Voila.