testing for dev kernel on xbox or not, use nxdk, based on Luke Ushers code example and nxdk hello sample.

main.c

#include <hal/debug.h>
#include <hal/video.h>
#include <hal/xbox.h>
#include <nxdk/mount.h>
#include <windows.h>
#include <stdio.h>
#include <string.h>

int main(void)
{
    XVideoSetMode(640, 480, 32, REFRESH_DEFAULT);

    debugPrint("Insignia Setup Assistant\n");

    // Hardware Detection (Retail vs Debug bios)
    if (XboxHardwareInfo.Flags & XBOX_HW_FLAG_DEVKIT_KERNEL) {
        debugPrint("\nDebug Bios Detected\n");
        debugPrint("Patching XboxHardwareInfo to retail mode.\n");
        debugPrint("Please note that this is temporary.\n");
        debugPrint("You WILL need to re-run this program after rebooting.\n");

        XboxHardwareInfo.Flags &= ~XBOX_HW_FLAG_DEVKIT_KERNEL;
    }

    // Sanity check: Make sure the HDD key is not all zeroes
    int valid_hdd_key = 0;
    for(int i = 0; i < 16; i++) {
        if (XboxHDKey[i] != 0) {
            valid_hdd_key = 1;
            break;
        }
    }

    if (!valid_hdd_key) {
        debugPrint("Nulled HDD keys are not supported!\n");
        debugPrint("This is a limitation of Microsoft's Xbox Live implementation.\n");
        debugPrint("Please don't NULL your HDD key.\n");

        debugPrint("\nSetup assistant will exit shortly...\n");
        Sleep(5000);
        XReboot();
    }
    bool saveFile = false;
    if (!nxMountDrive('C', "\\Device\\Harddisk0\\Partition2")) {
        debugPrint("Mounting error: Could not mount drive C: - No file will be saved.\n");
        saveFile = false;
    }
    // We detected a retail unit, so capture the keys
    DWORD dwType;
    DWORD cbResultLength;
    UCHAR SerialNumber[12];
    UCHAR OnlineKey[16];
    ExQueryNonVolatileSetting(0x100, &dwType, SerialNumber, sizeof(SerialNumber), &cbResultLength);
    ExQueryNonVolatileSetting(0x102, &dwType, OnlineKey, sizeof(OnlineKey), &cbResultLength);


    debugPrint("\n\nPlease use the following information to register your Xbox:\n\n\n");

    // We good, dump keys
    // TODO: Clean this up to be less ugly/hacky
    char buffer[4096] = {};
    sprintf(buffer, "Serial Number: %c%c%c%c%c%c%c%c%c%c%c%c\n\nOnline Key: %02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X\n\nHDD Key: %02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X\n\n",
            SerialNumber[0], SerialNumber[1], SerialNumber[2], SerialNumber[3],
            SerialNumber[4], SerialNumber[5], SerialNumber[6], SerialNumber[7],
            SerialNumber[8], SerialNumber[9], SerialNumber[10], SerialNumber[11],
            OnlineKey[0], OnlineKey[1], OnlineKey[2], OnlineKey[3],
            OnlineKey[4], OnlineKey[5], OnlineKey[6], OnlineKey[7],
            OnlineKey[8], OnlineKey[9], OnlineKey[10], OnlineKey[11],
            OnlineKey[12], OnlineKey[13], OnlineKey[14], OnlineKey[15],
            XboxHDKey[0], XboxHDKey[1], XboxHDKey[2], XboxHDKey[3],
            XboxHDKey[4], XboxHDKey[5], XboxHDKey[6], XboxHDKey[7],
            XboxHDKey[8], XboxHDKey[9], XboxHDKey[10], XboxHDKey[11],
            XboxHDKey[12], XboxHDKey[13], XboxHDKey[14], XboxHDKey[15]
        );

    debugPrint(buffer);
    debugPrint("\n\n");

    debugPrint("These keys are Xbox-unique\nSharing them WILL allow people to impersonate you online\n");
    debugPrint("PLEASE keep them private! We will ban shared keys.\n");

    if (saveFile) {
        const char *filePath = "C:\\XBL_info.txt";
        HANDLE fHandle = CreateFile(filePath, GENERIC_WRITE,
                                    0, NULL, CREATE_ALWAYS,
                                    FILE_ATTRIBUTE_NORMAL, NULL);
        if (fHandle != INVALID_HANDLE_VALUE) {
            DWORD bytesWritten;
            WriteFile(fHandle, buffer, strlen(buffer), &bytesWritten, NULL);
            if (bytesWritten == strlen(buffer)) {
                debugPrint("\nFile successfully written to %s!\n", filePath);
            }
            else {
                debugPrint("\nFile writing failed.\n");
            }
        }
        else {
            debugPrint("Couldn't open file.\n");
        }
    }

    for (;;) {
        Sleep(1000);
    }

    return 0;
}