Warnings w/ !$var

I recently installed PHP on a Windows 2000 server and brought over a few general PHP scripts (used on a Linux box), but have found a very annoying difference that I am wondering if I can get rid of. I us many checks in my programs with a simple !$var check -- which works find in Linux, but I get a Warning message out of Windows whenever it comes to this (but it does continue with the execution correctly). Is there a way I can tell PHP to not print out those Warning messages for !$var cases? I relize there is the isset($var) option, but this is not an option in some cases. Thanks for any help! Nick