I used X2.5035 (x2_5035_vOld_512k.bin), because it allows you to change the bios config from a config file on the xbox HD rather than having to edit the bios file and reflash it.
I read loads of tutorials (paranoid!), and used bits from all of them, but I couldn't find a recent one that matched what I was trying to do and was easy to use.....
However, once I got the basic steps sorted, it was actually very easy.
- softmod your xbox (loads of tutorials on that! Use Krayzie
- solder the two bridges (pictures here
, but ignore the flashing method described)
- create a 1Mb bios file from your chosen bios (I used x2bm)
- flash the bios. I used the net flashing utility in Resctoox
first time round, but have subsequently also used the Evox dash method (install Evox dash as an application, put the bios in /EvolutionX/BIOS, run Evox, select "Flash BIOS" from the menu, pick your BIOS from the list) and both work fine.
Hope this helps.