Can't completely remove FSX..Can't reinstall..

Hi, i was wondering if anyone could help me with my problem. I have bought and install FSX a couple of weeks ago, however recently i was unable to play the game all of a sudden.. when i tries to play, i encounter this msg "Error 1721: There is a problem with this installer package. A program required for this install to complete could not be run, contact your support or package vendor."

I tried to remove it via the control panel but the same message showed up. Rolled back occured and even rolled back could not be complete as another msg pop up " Error 1603 fatal error during installation.." i therefore have to manually deleted all the files and subfiles because i can't keep it hanging there as it takes up too much harddisk space. I managed to get back about 14gb.. however it seems something or some part of fsx is still in my computer because i can;t reinstall FSX. When i insert the fsx disc, i only have the options of either repair or remove but can't perform either as error msg will pop up. What can i do now?? Does any know or can advise me??? thanks alot!!