Yahoo Answers has been down for some type of "Total Makeover" and now it is up but running very slowly. That's why you haven't gotten much response to your question.
You forgot to mention WHICH version of OS X?
Don't mess with trying to use a DVD archive file on a FAT partition. Copy it to the OS X partition.
StuffIt is not the default application (after OS 10.2.8) for expanding a RAR file. Use the built-in Archive Utility in OS 10.5 or 10.6. Use the built-in BOMArchiveHelper in OS 10.3 or 10.4. Other good options are Unarchiver, UnRarX, and Zipeg. Search online for these. I remember using StuffIt Expander from OS 7.6 until OS 10.2.8 and we often shouted its name when it failed: "Oh, stuff it!" In those days, RAR files were rare (haha!), but we used StuffIt for those .sit files for which it was specifically designed. Nowadays, no one uses .sit files. The zip is the standard -- or should be -- for simple single folder packaging (with or without compression) and the DMG is the standard for large or multiple folder packaging. Both formats expand without any added software on any recent Mac and on most Linux systems. RAR is only useful for segmenting which poses some difficulties in both OS X and Windows.
NTFS partitions can be used as read/write with Snow Leopard. See the link below.
Mac OS X 10.2 to 10.5.x can read/ write to "Mac OS Extended (Journaled)" file system and FAT32 file system (Apple's Disk Utility will call this "DOS file system"). Mac OS X can read and copy files from NTFS file system but cannot copy, save, move, or rename files from NTFS drive volumes. You will be limitted to 4GB or smaller files on a FAT32 drive volume. To use HFS-Plus drive with Windows, install MacDrive. To use NTFS drive volume with OS X, install "NTFS for Mac" or a combination of "MacFuse" and "NTFS-3G". Links below.