I have tried several ways over the years and they have all resulted in wasted time, corrupt, unreadable files and loss of original data EXCEPT for 1. format both of your USB drives with the XBOX 360 leaving enough room not allocated to the XBOX for adequate functioning on your PC or XPORT (if you have it) but enough room to successfully save 1 content to the other and then 2. plug both USB drives into your XBOX 360 and transfer from the system storage device/drive options. This way was the only way that I have found to transfer all customs, audio/video settings and title update so the new USB was automatically recognized by PC, Party Buffalo and the game. to be on the safe side, copy contents from one to the other instead of “moving” so you have your back-up (original US:cool: should anything go wrong. I have, in a pinch, managed to copy customs from my USB drive directly to my hard drive and play the customs without a flash stick as long as I declined to connect to XBOX Live and skip the “download update” prompt at the launch of the game. If you accidently download title update 5 while customs are saved to your hard drive, the songs and the data will show up on your master song list but if you select to play a custom, you will get a “disk unreadable” error and either get kicked back to your song list or have to reset your game.
The thing that has made all the difference for me was to buy a USB 3.0 flash stick (monster) adjust your PC settings correctly so your power save features aren’t configured to run the USB port with speed restrictions, make sure you have a USB 3.0 port with updates and drivers and be mindful of the 256 bug. I have a 2000+ song library and I wipe flash drives often (whenever my sons mix up Rock Band and CoD) and I’m able to copy, clean, reformat and transfer songs back all within 10-15 minutes.
If you are a diehard like me, buy 2 cheap 20gb hard drives put RB3 title update 5 one 1 title update 4 on the other and then swap depending on if you want to play for leaderboard/score ranking (live) or just be able to access good customs. 20gb hard drives can go for less than a good flash stick on ebay/ craigslist.
