When un-installing FS 2004 - especially if there has been a problem - make sure that you delete the files in FLIGHT SIMULATOR FILES under your Documents directory in Windows. The un-install procedure does not do this and you may be faced with a screen message box at the startup of a re-installed FS2004 which reads AIRCRAFT INITIALIZATION FAILURE xxxxxx (being the aircraft name) CLOSE. Clicking on CLOSE shuts down the programme and you cannot use FS2004 at all.Microsoft were unaware of this when I emailled them - or was it one of their off-days!