You want one of these:
http://www.m-audio.com/products/en_us/FireWire410-main.html
Your software choice will depend on what program you are most familiar with. I've used the Abilton software. But I hear protools works much better.
As for hardware, get a motherboard with onboard firewire 800, Then concentrate on hard drive space, processor and Ram. You will want two drives. AN OS / software drive, and then a huge hard drive for writing music direct as you go. SATA is a must.