The simplest solution is to format your Windows partition as FAT32. But it's an older format that does not offer support for file and folder permissions or encryption, which means you have fewer options for securing your data. And with FAT32, you are more likely to encounter problems such as hard drive fragmentation, which can impact overall performance.
Finally, NTFS is a journaled file system, which provides greater error-checking options for the hard drive and reduces the risk of data loss if the computer is unexpectedly restarted.
If you want the advantages of NTFS and full access to your Windows files from within Leopard, you can install an NTFS driver for Mac OS X. There are two main options: MacFuse (a free port of the open-source Fuse tool that allows Linux systems to access NTFS drives) and Paragon NTFS for Mac OS X (US$39.95). Both are generally reliable solutions, though Paragon is more user-friendly, particularly for new or nontechnical Mac users.
The issues of accessing your Mac OS X partition from Windows are very similar. Windows does not have any built-in capabilities for reading the most commonly used Mac hard drive format types, which are variations on Apple's HFS+ format (also called Mac OS Extended).
In much the same way that MacFuse and Paragon NTFS allow full access to NTFS-formatted Windows partitions, Mediafour's MacDrive (US$49.95) allows Windows to access Mac-formatted drives and partitions, including the partition containing Leopard.
When using virtualization
What if you're using a virtualization tool instead of Boot Camp? Unlike Boot Camp's dual-boot approach, which requires restarting your computer to switch between operating system partitions, virtualization tools run Windows alongside Leopard on a single drive. Even so, accessing files and folders created in the other operating system can be tricky.