your "hd" is not in FAT-32.... your win partition might be, but I think your confused... or i am very tired LOL
FAT, NTFS ect, are file systems.
When INSTALLING Linux you can choose what type of file sys u want (FAT, FAT-32, ect) you want

Defraging ur windows partition wont effect ur RedHat partition though(i dont think) No, YOU CANNOT OPEN LINUX FROM WINDOWS. lol (but u can run Cygwin instead lol) However theres several ways to set up dual boot. Run a search
My favorite way is to make a bootable floppy
Hope I helped,
Al