It's not about the file format, it's about the disk format. The default format in Windows XP is NTFS, and OSX (10.3 or 10.4) will only read NTFS, not write to it. The default format in OSX is HFS Plus, which WinXP won't read or write. Both WinXP and OSX will read/write FAT32, but OSX can only see partitions less than 128 gigs. WinXP will only format a FAT32 partition less than 32 gigs. OSX will only format an entire disk FAT32, not partitions. Confused yet? :-)
If you can live with 32 gig partitions, you only need WinXP. Format your disk there, OSX will read/write it, and your Apple Lossless files will work in iTunes on either machine. If you want 128 gig partitions, you have to use other software. You can create partitions of 128 gigs in Windows 98, which WILL format a FAT32 partition bigger than 32 gigs. OSX will read/write these. You can also use a third party partitioning product like Partition Magic, which also will create and format FAT32 partitions of 128 gigs.
Bottom line is as long as both operating systems can see your hard drive, the Apple Lossless files will work in both Windows and OSX.
If you can live with 32 gig partitions, you only need WinXP. Format your disk there, OSX will read/write it, and your Apple Lossless files will work in iTunes on either machine. If you want 128 gig partitions, you have to use other software. You can create partitions of 128 gigs in Windows 98, which WILL format a FAT32 partition bigger than 32 gigs. OSX will read/write these. You can also use a third party partitioning product like Partition Magic, which also will create and format FAT32 partitions of 128 gigs.
Bottom line is as long as both operating systems can see your hard drive, the Apple Lossless files will work in both Windows and OSX.