The only way to fix this, is to go into task manager, find the romfsbuilder/extracter and there should be a drop down menu. While you are extracting or building the romfs, if it gets stuck on 'prompting save', that means you clicked off of the program.If you are using Reggie Next to edit levels, put the Unit folder (In romfs) into the courses folder and then click the option 'Change Game' in the FILE tab and select NSMB2 if it isn't selected already! It won't work otherwise!.If the braindump fails, it probably means that you don't have enough space in your sd card!.Now, save the configuration and load the game! Whatever editing you did should now be there! Your Welcome! Select the one that says 'sd -> romfs' or something like that and make sure it says yes. Select NSMB2 and HOLD L while it loads! There should be some options there. Put your sd card back into your 3DS, and load up hans. If there isn't already, make a folder on the root of your sd card called 'hans' (no quotes) and put the. romfs (I told you that title ID was important!).

Same thing as before, select the romfs FOLDER and save as. Now, once your finished editing, open up packhack and run the app called ROMFS_BUILDER. Now do what you want with the files! Edit the levels with Reggie Next or CoinKiller, replace some music, make some textures, whatever. So just don't click off of it! It only takes like 2 minutes anyways. A common mistake people make is that they click off the program and the save as. Now that you have your romfs, time to turn that into something we can use! In the packhack folder there should be a application called ROMFS_EXTRACTOR, which is what we are going to use to turn the romfs into a folder. Right now all we need is the romfs, so save that to your computer. BE PATIENT!! Once you are done, put your sd card into your computer and there should now be a folder called something like '0000007000ae00' or something like that (remember this as it is important for later!!), with your romfs and exefs. Using braindump is very simple! Just put the folder into your 3ds folder where you keep your apps, select NSMB2, and run it! Please note this does take a while to do. So the first thing you need to do, is get the actual course files to edit. Packhack - I couldn't find a link (its at the bottom of the post)

How to play rom hacks using hans