How to make a new polygon/feature from a point which is NOT a centroid?

Spent all morning searching help sites and digging through the FAQs and worksheets but have failed miserably.

I am an Arc novice so I hope this isnt too much of a "newbie" question but I'm trying to work out how to make a new polygon/feature from a point which is NOT a centroid?

I have a series of points where the Easting and Northing listed represents the lower left hand corner of a 200m square. I know how to make a circular buffer which I can convert to a square with the Feature Envelope to Polygon tool but this isnt really what I want.

Any ideas?