External hard drive question

I have just received my new Western Digital 1TB My Book and have noticed that it is formatted as FAT32.  I have seached the net (for a whole 4 mins and gave up cause I have to go out) and didnt find anything that jumped out to say why it was farmatted this way.  I'm not a hard drive expert but I'm wondering why it isnt NTFS.  Should I reformat the drive or just leave it as it is?  Will I gain anything?

The use of the FAT32 format is to allow the drive to be downwards compatible with lower versions of Windows than XP and other OS. If you plan to use it with XP or Vista only, you can safely reformat the drive to NTFS, though as I said it will be accesible only to Windows machines.

Fat32 has a file size limit of 4GB. Most external drives you purchase will be Fat32 by default for compatibility issues as mentioned by TekMon.

For 1TB it's not the best idea to use Fat32.

Thanks   Looks like I need to format it then