There are a limited number of modifications you can do, but most of them would require the use of a modchip and/or significant technical skills. Some common modifications done to Xboxs include:
your profile!
you need a upgrade
Yes.
There is only 1 thing to upgrade on a Xbox, that is the hard drive.
Downloading an Xbox 360 upgrade onto a CD requires a few simple steps: Create a new folder on your desktop and call it Xbox 360 Upgrade. Visit the Xbox website and download the upgrade file saving it into the folder you just created. Insert the blank CD into your CD drive and open the CD-burning software on your computer. Load the upgrade file from the Xbox 360 Upgrade folder into the CD-burning software. Burn the upgrade file onto the CD. Remove the CD from your CD drive and insert it into your Xbox 360 console.Once the CD is in your Xbox 360 console the upgrade process can begin. Simply follow the on-screen instructions to complete the upgrade process.
from what??
You can upgrade to gold by clicking "upgrade to gold" in the xbox guide. You can try to see if it will accept your local username, if not it's already taken.
only on slim
buy a new hard drive?
Yes xbox live is completely free except if you want to upgrade to gold
When a upgraded Xbox 360 comes out, you need to buy it at the full detail price. There is no upgrade package on the Xbox 360.
You don't only some original xboxs games work on xbox 360, usually the last ones out for the original xbox.