Unusual Question- compiling a kernel, linker troubles!

[3ddev]

I decided to take a little break from coding games right now. Just for the fun of it, I decided to try writing my own home-brew kernel. I am compiling the kernel with mingw. Here is the complete list of commands that I am using. It includes NASM for the assembly code:

C:\MingwGCC\bin\gcc.exe -Wall -O -fstrength-reduce -fomit-frame-pointer -finline-functions -nostdinc -fno-builtin -I./include -c -o main.o main.c
C:\Osdever\NASM\nasm.exe -f aout -o start.o start.asm
C:\MingwGCC\bin\ld.exe -T link.ld -o kernel.bin start.o main.o

GCC compiles fine, but ld.exe creates this error:

start.o: file not recognized: File format not recognized

I have been using MingW with Graphic Libraries and wxWidgets in Code::Blocks for years. I have never experienced this problem before. Can anyone help?

PS. For those curious about making their own kernel and OS, go to http://www.osdever.net.
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