Can't get aluminium front door off

My house has a very old aluminium glazed front door, due for replacement some time but not just yet.
It appears to be held in place by two vertical pins into the frame, one at the bottom and one at the top.
The mechanism at the top is a bit sloppy, causing problem with shutting the door and with draughtproofing, so I tried to take it off to investigate.
I found one hole in the door, a few inches below the top, at the hinge side, in which I could see the end of a grub screw pointing upwards at about 45 degrees. Tightening or loosening this screw had no apparent effect, and I tightened it so much it fell out the other end, and is now presumably inside the door. This does not appear to have caused any further problems.
The frame is screwed in on all four sides, one of which I cannot access because the door is in the way. I tried unscrewing the top section of the frame to see if I could pull it out with the top of the door, but it was apparently invisibly fixed firmly to the two side pieces and would not budge.
Chris Melluish

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