Hi buddy. Could be a number of things - but all quite simple! you don't mention the model but if its something you fancy trying yourself - heres what to do: First you will need to access the mechanism by taking off the door panel - follow this guys instructions -they are excellent -http://wiki.answers.com/Q/How_do_you_remove_the_driver_door_panel_of_your_1998_r_reg_ford_fiesta
Got the panel off? Good! Peel away the insulation/silencing foam - carefully - you don't want to rip it so take your time. start at the top right - work your way to the bottom then to the left. You will eventually find a large void with your window glass sitting behind and hopefully on the winder mechanism. Take a look - the mechanism works by a pulley system - a wee motor winds in the metal wire which is attached to a holder - of which the glass sits on. There should be two screws holding the glass holder onto the mechanism. Check if they are attached and then check that the wire is still in one piece - from what you say it sounds like this might have snapped. Again if this is the case you can easily pick up a spare part at your local scrappys (I recommend www.1stchoice.co.uk - the scrapyards come to you and you can compare their prices!) or ebay. Good luck!
premster
October 2008