ok so i'm pretty sure that i could do this but i want to ask just in case.

I have 2 modded xboxes. one of them has my "favorite" modchip but only the retail HDD. The other has a really old mod chip but my upgraded HDD. My question is can i just swap the 2 HDD's and run the xboxes like nothing's different? or do I have to reformat the Hdd's to do that

thanks

Two things to consider:

1. Both hard drives have to be unlocked.
2. Both hard drives have to use the same partitioning scheme, or to be more correct, both modchips must be running a bios that uses the same method of allocating extra space.

To expand on #2: If your large hard drive is over 120gb both bioses should have a matching minor version number of either .67 or .06. I suggest checking the system info in XBMC or your favorite dashboard, it should show you there.

You should be able to swap them out. Really it depends on the software you set the HDs up with.

For example:

Xbox1 boots from C:\default.xbe

Xbox2 boots from C:\Xboxdash.xbe

You may have problems. Look at the files you have and that will help you see what is going on in the Xbox.