dot dot slash slash

This is strange. I haven't had any trouble in the past executing Windows .exe files via a webserver using PHP's exec command when I specified the path to the executable with forward or backward slashes a la: ../../bin/MuseScore/bin/mscore<br/> or ..\..\bin\MuseScore\bin\mscore but now I'm getting this error: '..' is not recognized as an internal or external command, operable program or batch file. To fix the problem, I now have to use double backlashes even from the Windows command prompt like so: ..\\..\\bin\\MuseScore\\bin\\mscore I have no idea what's changed all of sudden on both my local computer/webserver and my Windows VPS. ... er, I meant to write "computer\\webserver". ;)