Ok this is my 1st time at this and need some questions answered if it's possible.

Friend of mine had a old orignal Xbox 360 (203W) that went RROD, he's not the type to open things up and try to fix it so he just gave me the box (no HD, memory card, power cable, or video cable) and purchased one of those kits to fix RROD. Anyway had a friend that had the power cord for the 203W 360 and got everything running, now i want to play it but have no storage at all. I was thinking about buying 20Gig HD and buying a larger WD Drive to replace it but my question is with all the bans they did for the firmware hacks will the harddrive hack be detected and are they banning people that do use it on Xbox Live?

Another piece to add to this WalMart was running a special on the Arcades not to long ago. Buy a arcade and get a $100 gift card from Walmart. So I bought 1 and then another later. One of the Xbox's I bought didn't prompt for offering the $100 gift card even though it was still within the dates they were offering it so they did two transactions. Since the serial number of the 360 wasn't registered with the gift card it's a free $100. Now the other one I was gonna sell on Craig's list but if I keep it that means a free xbox. I could mod the old one and keep the new one legit but I lack the storage space. So can I buy a used 20Gig and do the HDD hack and use a larger drive but use it for both systems without being banned?