the monster builder is really cool and so is the character builder - but as Iapetus says for a 4e game ... but the good old monster manuals are great too Although you'll have some conversion to do if you have a 3e monster and a 2e players book ... I'd think about upgrading your game to 3.5e or Pathfinder (also 3.5 as far as I know) or 4e. Then again - when I started gamemastering I just made my own rules based on old wargames - that worked fine - its the setting/mood/etc that is the important part anyway