Guide_3DS/_pages/ja_JP/include/id1-check.txt

This occurs when you use multiple SD cards with the same 3DS and then merge the SD card contents together. Both are "valid", but the 3DS can only read one at a time.

You will need to determine which one contains your data. First of all, back up all of the folders, in case something goes wrong:

![Backup ID1](/images/screenshots/troubleshooting/backup-id1.png)
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Now, delete all but one of the folders from your SD card. Generally, you will want to delete the **smallest** one(s), as the one with all your data will probably have more space occupied. You can compare which folder is occupying more space by right-clicking it and clicking "Properties":

![Properties prompt](/images/screenshots/troubleshooting/rightclick-properties.png)
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![Which to delete](/images/screenshots/troubleshooting/compare-id1.png)
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Your SD card should now look something like this:

![Just enough ID1s](/images/screenshots/troubleshooting/correct-id1.png)
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Now, put your SD card into your 3DS and turn it on. If your data is still there, you deleted the right folder and have now determined your correct ID1. If everything has disappeared, go back into the backup folder that you made earlier and try the other folder.