When trying to create a bootable media on a stick with more than 32 GB capacity you get an error message "Media cannot be formatted" or bootable media is created, but the system does not boot from it.
Be cautious to use any sticks larger than 32 GB capacity when you want to make sure that you can use them as a boot device, or to be recognized in your BIOS / UEFI firmware. Most hardware cannot correctly handle USB sticks with more than 32GB capacity, which leads to the bootability issues. This is especially the case when you are using such a large stick in UEFI mode, which needs to be formatted with FAT32.
Official information about FAT32 limitations is available here (applies not only to XP).
If you need an USB stick to make it bootable or to flash your mainboard firmware, make sure to avoid an USB stick larger than 32GB size or consider its limitations. Pretty usual 8 GB or 16 GB are enough to serve these tasks.