AFAIK new 120gb hdd's in stores comes with a data transfer cable, I'm not sure how it works but it doesn't need a memory card. So you could look for one of those, or get a memory card indeed.
Here is how to do it:
Quote:
Question: How To Transfer Data from 20GB HDD To 120GB HDD
Whether you upgrade to the Elite from the Premium or simply buy the 120GB HDD separately, transferring your data from the small one to the bigger one is easy. Find out all about it right here.
Answer: To transfer data between the 120GB hard drive and the 20GB hard drive, you need a special transfer cable from Microsoft. When you buy the 120GB hard drive separately for $179.99, it comes with this cable. However, the Elite does not come with the transfer cable.
How To Transfer Data From 20GB to 120GB HDD
1. Connect your 20GB HDD to your new Elite console
2. Turn Elite system on and make sure a controller is recognized
3. Connect large end of the transfer cable to the 120GB HDD
4. Connect USB end of transfer cable to a USB port on your Elite console
5. Insert Hard Drive Transfer Disc into your Elite and follow the onscreen instructions
6. When the transfer is complete, you disconnect the 20GB HDD from the Elite and connect the 120GB HDD and you are all set
The transfer process can take up to an hour depending on how much stuff is on your 20GB HDD. Be patient.
If you are using the stand alone 120GB HDD with your Premium system, the sequence is the exact same other than the fact your 20GB HDD is already connected to the system.
It must be noted that this is a one time, one way process. You can only transfer from a 20GB to a 120GB HDD once, because after that one time the data on the 20GB has, obviously, been erased. It also can only go in one direction, from 20GB to 120GB only. Also, since Xbox Live Arcade games and video marketplace items are tied to your gamertag and the first system they were used on and not the hard drive, to use these items on the new system you will have to be connected to Xbox Live or they won't work. This is a minor inconvenience, but most people with Xbox Live are connected constantly anyway, so it isn't a big problem.
And now your 20GB HDD is clean and can be used on a different Xbox 360, and your 120GB HDD has all of your old data on it. Enjoy.
Taken from:
http://xbox.about.com/od/xbox360faqs/f/ ... ferfaq.htm All you need to do is get that cable =]