Why is my burning software is a gray imgburn

I just installed a recording software called imgburn, it found that the icons are displayed in gray, following a log, and the name of the yellow exclamation mark!
W 09:41:33 Drive D:\ (FAT32) does not support single files> 4 GB in size.

W 09:41:33 Drive E:\ (FAT32) does not support single files> 4 GB in size.

W 09:41:33 Drive F:\ (FAT32) does not support single files> 4 GB in size.
Why ah?