changing Kernel while keeping current Rootfs

I want to change current kernel on Tiny4412 (I have a new zImage file).
It's so simple. You put the new zImage and a rootfs.img in the SDcard and
boot board with it and it overwrites current kernel and rootfs. But I dont
want it to overwrite my current rootfs installed on the board because I
have already made lots of changes into it and I want to keep them. 
So how can I stop this from happening? 
Can I just delete rootfs.img located in SDcard so it wouldn't find it and
overwrite it. Does that possible?

for Mini2440 there is FriendlyArm.ini file. commenting
Rootfs=images/linux/abc.img with "#" does the job. 
There may be similar way for Tiny4412.

Thanks Sunny !
Good idea. Hey here's a question. If I changed Kernel and not changing
RootFS then would you say I don't lose any of my files and configurations
and other system files like /etc/init.d/rcS or ifconfig-eth0 or
wpa_supplicant.conf and ... ?
I mean which directory and files are going to change by changing Kernel? 
I mean after all some files have to change, right? Or all the files belong
to RootFS area? If it is so then what does changing the Kernel do? 
Unfortunately I don't know the relationship between Kernel and RootFS very
well!