When to choose FAT OR NTFS?

Many of my friends generally confused whether to choose Fat or Ntfs. ...while installing windows so through this thread i will try to esplain when to choose Fat and Ntfs?
ok so let us start..!!!!
For most users running Windows XP, NTFS is the obvious choice. It's more powerful and offers security advantages not found in the other file systems.

The NTFS file system, introduced with first version of Windows NT, is a completely different file system from FAT. It provides for greatly increased security, file–by–file compression, quotas, and even encryption. It is the default file system for new installations of Windows XP, and if you're doing an upgrade from a previous version of Windows, you'll be asked if you want to convert your existing file systems to NTFS. Don't worry. If you've already upgraded to Windows XP and didn't do the conversion then, it's not a problem.You can convert FAT16 or FAT32 volumes to NTFS at any point.

Now there must be question in your mind !!!When to choose Fat?
Okk
if you're running more than one operating system on a single computer.
You will definitely need to format some of your volumes as FAT. Any programs or data that need to be accessed by more than one operating system on that computer should be stored on a FAT16 or possibly FAT32 volume. But keep in mind that you have no security for data on a FAT16 or FAT32 volume—any one with access to the computer can read, change, or even delete any file that is stored on a FAT16 or FAT32 partition.

If you have further queries then feel free to ask....?I will try to clarify