Do you know if your model supports FAT32? If so, use a card reader and format FAT32. If not, you may have to partition the drive. I don't know if a microdrive can be partitioned.
Edit: I have been looking around, and have found that you might not be able to access the full capacity of the drive. If you bump the cluster size up to 64k, you may have access to 4GB of the drive's capacity. Try the FAT32 format first.
A google search unearthed this tool you might want to think about trying out:
pocketnow.com - Reviews - Softwinter's StorageTools
AND BE SURE TO BACK UP ANY FILES ALREADY ON THE DRIVE!
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