i have a softmod xbox with a 120gb, and now a want to upgrade my harddisk for a 250gb HD could my xbox handle just upgrading the bios or i'll need to install a chip?

Not exactly sure what you're asking but it sounds like you should check out the Softmod forum for this. You should be able to run a BIOS through your softmod that'll accept the larger drive but I'm really not too informed as far as softmods go.

Good luck.

thanx