On the Windows 7 Format wizard, there is always a file system that is noted as
Why is there a default file system? What is it exactly?
'Default' in this case is 'decide for me depending on the type of device' - where type of device is being either an internal or external drive and whether its a high or low capacity device.
If you do it on a memory stick or external hard disk, it'll recommend FAT32 or exFAT in most cases for compatibility with other devices.
If you do it on an internal hard disk, it'll recommend NTFS.