Just threw this together... requires WSHPipe(). Only tested with XP, so I can't be sure it works 100% with other OSs.
Code:
 
? diskspace("C:")
 
function $diskspace($drive)
  dim $lines
  $lines=wshpipe('%comspec% /c dir ' + $drive + '\',1)
  $diskspace=join(split(split(trim($lines[ubound($lines)-1])," ")[3],","),"")
endfunction


{edit: Dang it... jumped the gun again... I thought you wanted free space... not total.}

Edited by Allen (2006-09-14 06:25 PM)