PC to Mac switch - trepidation

I have a 1TB My Book that was used on a PC until I bought an iMac.  I hooked it into the back of the Mac and it seems to work.  However, I get the impression that I need to reformat the drive for Mac OS.

  1.  Is it true that I need to reformat and then configure for the Mac?

  2.  What happens if i don’t (it seems to be working so far)?

  3.  I know everything will be wiped when/if I reformat the drive.  Do I then have to download all the drivers, etc.?

Thanks for your help.

Was the other PC Windows or Mac? If the drive is formatted for Windows it will be read only from the Mac. You can get NTFS-3G http://mac-free.com/download/NTFS-3G.html  and it will work on both. If you no longer intend to use on Windows it would probably be best to reformat for Mac. That will wipe out all data on it now.