well here are the specs u need:Halo PC Requirements:
CPU: 733 MHz
128MB RAM
HDD Space 1.2GB
Graphics Card: 32MB / 3D T&L capable(u can also use integrated graphics, some are capable some are not)
pretty low requirements but then if u wanna try out custom edition, with the new maps and junk...
u need:
1.4 ghz Pentium 4 or Athlon XP
512- 1 GB min RAM
8 GB Hard Drive
With All the AI u may need a geforce 6 or 7 series or radeon x1000 series
u might just wanna settle with the 200$ and get a decent system for 200$