This code seems to hang the computer:
 gotoxy(0,0);
 clreol();

There's at least one bug in the code shown, as well:
gotoxy() coordinates are 1-based, i.e. gotoxy(0,0) is an illegal
call. Chances are that this confused clreol() into an 
endless loop.

The info topic on gotoxy explained that the upper left corner of the text window was (1,1), not (0,0) as I thought. I apologize for taking up your time...