downgrade to older rom / flash back to older rom ... how??

[dragonetti]

can somebody please tell me how to flash the qtek 9090 back to a previous rom, to be more precise:

I created a "NK.NB1" file using this tool:
http://wiki.xda-developers.com/index.php?pagename=XDAtools
But how can I put this rom back into my qtek 9090??

I used the search using the following key words: "downgrading" / "old rom" / "flash" ...

But I couldn't find a satisfying awnser...

thank you!