Pretty much everything. Dunno if you needed a Hard Drive or not. One of your friends might have an extra laying around and I think I saw you say that you could get a copy of Windows from a friend. Now its not the Top Dog system but it will run games fairly well. And you can ofg course upgrade it as need be. Its how I started. Something Simple and basic. Along the line I have upgraded alot.
I started with a E5300 Celeron Dual Core Processor, 2GB PC5300 ValueRAM, ATI 2600HD GPU, Power Up! Bad airflow "Gamers" case, and a Biostar p4m900-m7 fe Mobo. It was horrible.
I have what you see in my Sig Rig now.
If you can manage to sell your XBox and get some extra cash that will open alot of doors to a high step of stuff. But only sell your console if you don't use it.