Installing a new Debian OS to internal memory?

[Catscrash]

Hi,

I managed to kill some init-kernelfiles on the internal memory when I wanted to try something out ;-) , leaving me with an unbootable device, now I could of course (since uboot is still working) just install another system to an usb-pen but i would rather install a new debian to the internal memory. I didn't find any information on how to do that on the internet, is there a way or do I have to use an external memory now?

Thanks
Catscrash