My Bootcamp Windows system can't see my Mac files?
The reason is that with the latest version of OS X, the internal drive is converted to a Core Storage volume, rather than the simple HFS+ volume you presumably had on your old computer. Apple still hasn't rolled out support for this in many areas, Windows included. You won't be able to access your files directly anymore from within Windows until Apple gets around to implementing Core Storage in Windows, if they even have plans to do that. The only solution is to use an external drive or create another partition formatted as exFAT or FAT32 as a neutral location that can be accessed by both operating systems.