Put an area rug over it.

Probably replace it. By the time you try to work with it dollar wise, you maybe could put down a new rug.

Replace it. It's the old adage you can't make a silk purse... For a single room you can often find carpet remnants from other installations that will fit and are really inexpensive. Visit your local carpet supplier. They love selling remnants! Keeping the carpet pad and just replacing the carpet will save a lot of the cost too!

An upgraded carpet pad can make an inexpensive carpet feel like a million bucks and it's so inexpensive.

agree, check for remnants.