Halo 1 slow on Windows 7?

I just bought a new Windows 7 computer:

Intel Pentium G3240 3.1GHz Processor (3 MB cache)
4GB DDR3 RAM
1 TB 7200 rpm Hard Drive
Windows 7 Professional 64 Bit installed
Intel HD Graphics

I downloaded the new update for Halo in order to play online again since the gamespy servers shut down. And now it tells me that my computer's hardware is below the reccomended minimum specs. How can it be that this brand new computer can't run this old game? I've had the exact same computer before and ran it with no problems. Please help.