@jaclaz This is very interesting question . I think () may change own type corresponding context of command grub4dos. Try this commands: map () (hd1) map --hook cat --hex --length=512 (hd0)+1 cat --hex --length=512 (hd1)+1 cat --hex --length=512 (hd0,0)+1 cat --hex --length=512 (hd1,0)+1 ls ()/ root () geometry (), geometry (hd0), geometry (hd0,0) And as I know grub4dos manual may be not correct sometimes... or do not have additional information about using commands. I also read chines forums, ChangeLog_GRUB4DOS.txt (new syntax "map"-command coming soon, current on testing stage). 2009-11-11 let PXE_BUF use BUFFERADDR. cancelled (hd+) support. added (hd) and (hd-N) support. http://nufans.net/grub4dos/tinybit/