LT = left trigger. Im sure you can figure RT for yourself.
The BIOS you are using is stored on your xbox modchip, or on your TSOP if it has been flashed. The C:bios directory is just where you put a new BIOS that you want to copy onto the modchip/TSOP for use. AFAIK You can tell what BIOS you are using by copying the BIOS hash info (from a thread somewhere - do a search) into your evox.ini file. Evox will then tell you what BIOS you are using.
What modchip have you got?