I don't have a great need to root my phone, not for just this, and I don't want to wreck it, I paid full retail price for it. I'm not confident in doing it, phones and computers are a personal interest, not my expertise or profession.
The Screen Grabber app works just fine on my Bionic.
As I mentioned, screen shot apps such as Screen Grabber work fine with some unrooted phones, but not with others. There are a lot of software differences from phone to phone, even from the same manufacturer. The only way to get apps like that to consistently work across most phones is with root. If you don't want to root, and have not been able to find another third-party app that happens to work with the phone, your only guaranteed option is to press and hold the power and volume down buttons for a couple seconds.