If you expect to have files greater than 4GB you will need to change your drive format to NTFS. Microsoft provides a utility called “Convert” which allows you to change the format to NTFS with your files in place. You can find instructions for Convert at this link: http://technet.microsoft.com/en-us/library/bb456984.aspx

If you would rather re-format your external drive, proceed as described below.

WARNING: Any data on the drive will be erased in this process. 
 Please backup any data on the drive before proceeding.

Follow these steps to format your drive for Windows: 

1. To remove the existing disk partition, right click on My Computer (Computer for Vista) and select Manage.
2. On the next screen select Disk Management.
3. Find the listing for the external hard drive in the lower middle portion of the window.
4. Right-click on the box to the right of the drive listing (Disk X) and select Delete Partition.
5. A message will ask you to confirm that "All data will be lost." Be sure you wish to do this. If so, then click on Yes.
6. Once complete, the box will show "Unallocated".
7. To create a new partition, right-click on My Computer (Computer for Vista) and select Manage.
8. On the next screen select Disk Management.
9. Find the listing for the external hard drive in the lower middle portion of the window.
10. Right-click on the box to the right of the drive listing (Disk X) and select New Partition.
11. Accept all of the default parameters.
12. The formatting will start and will be busy until complete. You can monitor the progress in Disk Management.

Once the formatting is complete, the external hard drive is ready for use.