You cannot just rename a .jpg to .bmp . You need to use an image editor.
Unlike other manufacturers that accept JPGs or PNGs, Lenovo’s BIOS and system utilities (like the Registry or System Properties) are notoriously picky. Use the wrong size or color depth, and you will end up with a black box, a stretched mess, or no logo at all. lenovo oem logo bmp 120x120
Do you have a different size requirement for a different brand? Let me know in the comments below. Disclaimer: Modifying system files requires administrator privileges. Always back up your data before making system changes. You cannot just rename a