To find where Scilab is installed (Windows)

in Windows registry, to detect scilab 5.3.0 and more:

On Windows XP 32 bits (& Vista/Seven)

[HKEY_LOCAL_MACHINE\SOFTWARE\Scilab] 
"LASTINSTALL"="Scilab-5.3.0"

[HKEY_LOCAL_MACHINE\SOFTWARE\Scilab\Scilab-5.3.0]
"SCIPATH"="\"C:\\Program Files\\scilab-5.3.0\""

On Windows XP 64 bits (& Vista/Seven)

[HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Scilab]
"LASTINSTALL"="Scilab-5.3.0"

[HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Scilab\Scilab-5.3.0]
"SCIPATH"="\"C:\\Program Files (x86)\\scilab-5.3.0\""