The mechanism for winding the glass up and down has one of the runners rusted off therefore the window is not able to be raised or lowered. Is there a way of repairing the runner or does the whole of the glass have to be replaced?

IanL2009, September 2009

Guessing that you're talking about the short guides (about 50 -75 mm long) which are spot welded to the glass channel. These guides engage the rollers on the regulator mechanism.
If they are rusted off, then you can easily replace it and a new glass channel is available - try "Mdabitec" - on ebay.

JD, September 2009