Adding module into existing kernel

Hi!

I'm using Fedora Core 2 and I end up getting a small problem when I try to add ntfs module to let fc2 read ntfs partitions. When I compile the kernel, compile the module, and load the custom kernel I am able to mount the partition. However, if I load the stock kernel I am unable to mount the partition because it says that the ntfs.ko module cannot be found. If I do modprobe or insmod to load the ntfs.ko file from the custom kernel I get a "Invalid module format" error. Shouldn't I be able to load the module? Am I missing something? I would appreciate any help.

Thanks,
euix