public bool RemoveDrive(char drive)
{
drive = char.ToUpper(drive);
if(drive < 'A' || drive > 'Z') {
return false;
}
// check if the drive is already in the category
if(drives.Contains(drive)) {
// delete all occurrences
do {
drives.Remove(drive);
} while(drives.Contains(drive));
return true;
}
return false;
}