Code did not work on Explorer but worked on PHP coder.

hi I tried a php code below: <!doctype html public "-//W3C//DTD HTML 4.0 file://EN"> <html> <head> <title>Title here!</title> </head> <body> <? // Full sys path to count.txt $counter_file = "c:\count.txt"; // Puts the file lines into $counter_file_line array $counter_file_line = file($counter_file); // adds one to the number in the [0] array or the very first line $counter_file_line[0]++; // opends the file and then writes the new number and then closes it $cf = fopen($counter_file, "w"); fputs($cf, "$counter_file_line[0]"); fclose($cf); // prints out the full count echo "$counter_file_line[0]"; ?> </body> </html> whe I run this sample in "php coder" it worked. But when I run on Internet exoplorer it did not work. empty screen appeared. why? not: I have using windows 2000, IIS5 and PHP4.