Is the SD card in the Yun ?
The Yun supports FAT16, FAT32, EXT3 and EXT4.
Perhaps you could use FAT32.
Windows XP is not longer supported, you should get a newer operation system.
There are drivers for other file systems, I have used them a few times, but they didn't work very well.
http://lmgtfy.com/?q=windows+xp+"file+system+driver"+ext2+ext3+ext4