disk_free_space and disk_total_space works for only one drive

I wrote a script to check disk usage. Here's the meat of it: $free = round(disk_free_space($partition) / 1024 / 1024, 0); $total = round(disk_total_space($partition) / 1024 / 1024, 0); echo "$partition: $free MB free, $total MB total\n"; With $partition = "D:", it works fine. Note that the script itself is on D:. With any other drive, it just shows 0 for $free and $total. This script works fine on Apache and Linux, but not with IIS and Windows. It does work using PHP on the command line in Windows, though. Could it be a permissions issue? I'm using PHP 4.3.10, IIS 6.0, Windows Server 2003. Thanks in advance. --df