Update your game to MechCommander ver 1.8 and follow the directions below for these cheats to work.

In the directory where you installed MechCommander, rename the file windows.fit to ixtlriimceourl then use the following
codes.

During the Logistics Phase type in

  poundofflesh: Adds 1,000,000 resource points
  rockandrollpeople: Removes drop weight limit on current mission
During a mission type in

  deadeye: Maximum gunnery skills on all MechWarriors for current mission
  glennrocksthehouse: (at the start of a mission) completely salvage destroyed Mechs
  getsalvage: (at the start of a mission) completely salvage destroyed Mechs
  lorrie: Repairs damage to armor and weapons
  lordbunny: Unlimited instantaneous artillery strikes (Press B and left-click to use)
  mineeyeshaveseentheglory: Reveal entire map
  osmium: Makes all your units invulnerable
  Ctrl+Alt+W: Successfully complete current mission
  framegraph: Displays frame rate