Hello and welcome to the forums - thanks for joining
You could try an app like
this , but I know that on the recent update on the Desire HD, the ability to take a screenshot was integrated (by briefly pressing the power button, followed by the home button).
You could also check with other users of the same phone in the
HTC Inspire 4G - Android Forums sub-forum.
I am sorry, but I'm not actually sure about sharing a photo on someone's wall on your mobile, but someone in the Inspire 4G sub-forum may be able to advise!
Hope you find the answer you need
