okay explanation time:
you have brought you 2.6 ce. It comes preflashed with Flashbios. Flashbios is what allows you to download a full hacked bios to your chip. What you are trying to download from the Xecuter site is flashbios - which is already on your chip, so will not do you any good. By the way it's not you - the download for that bios is not working properly.
What you need to download is a bios called Xecuter 2 5035 and is availible from a place called xbins.
Here is a link to a tutorial on how to gain files from xbins:
http://www.xbox-scene.com/articles/xbins.php
be careful when flashing the bios as there are two versions of the bios. One for version 1.0 - 1.5 xbox's and one for version 1.6/1.6b xbox's. make sure you know what xbox version you have and flash the correct one.
also a good guide on using flashbios can be found here:
www.teamxecuter.com/flashbios/