Changing to NTFS in Lion

That is not possible. OS X can not format a drive ntfs. You'll need a windows computer for that. Note that once you do that mac os x will no longer be able to write to that drive. It can still read from it but can't write to ntfs formatted drives.

The native Mac OS X drive format is HFS, NTFS is a Windows format that Mac OS X can read but not write to.

To format a drive HFS, assuming the drive is connected to the Mac, open Applications, Utilities, Disk Utility and select the drive from those shown in the left sidebar. Then in the main DU frame, select Partition from the buttons in upper center of the window. Determine if you want more than one partition, and if so choose the number of partitions. Click the first partition, then just accept the defaults, Mac OS Extended (Journaled) and a GUID partition table. Then Apply to erase and format the partition. If you choose to setup more than one partition, follow that for each partition.

Maybe you didn't read the op post? He wants to change a external To NTFS. No where does he mention formatting it to the mac format.

Not necessarily, the OP may not have actually meant NTFS and may have been thinking of the Mac OS X format...happens regularly on here.

OS X does not have native support for writing to (and therefore formatting a drive as) the NTFS format. However, this is somewhat possible to do on an Apple system.

The first option is to get a FUSE implementation of NTFS, which instead of having a kernel-specific driver, offers the filesystem support as a plugin (FUSE stands for "Filesystem in USErspace). I am not too certain of the development status of current builds, but these have offered rudimentary options to format a drive as NTFS.

The second option is to use a virtual machine and set up Windows or another OS that fully supports NTFS, and then use that to access the external drive directly and format it.

The last approach is to install Windows in Boot Camp and likewise use that to format the drive.

If you install Paragon NTFS, you will be able to read/write NTFS drives, and format them as NTFS from within OS X.