Why can't Dell notebook legacy be changed?

The method of transforming uefi into legacy in BIOS of Dell computer;

1. Press F2 to enter the BIOS, press F2 to enter the BIOS interface, and switch to secure? On the startup page, select Secure Boot Enable and press Enter to change it to Disabled, and then turn off Secure Boot. When installing win7, it must be closed, and uefi cannot be changed to legacy traditional mode without closing it, as shown in the figure; ?

NOTE: Remember to apply BIOS changes to Dell laptops at every step.

2. Switch to sercurity to ppt? Remove the tick mark in front of PPT on the right side of sercurity, as shown in the figure below;

2. Switch to the advanced startup option, and check the Enable Traditional Option rom option on the right to enable traditional mode support, as shown in the figure below;

3. Pay attention to the hard disk mode when installing win7. If it is raid hard disk mode, remember to switch to system configuration and change the sata operatior hard disk mode to ahci mode. Otherwise, a blue screen 0x0000007b will appear when installing win7, as shown in the following figure;

4. After completing the above operations, we can see that UEFI can be changed to the traditional mode in the options on the right side of the boot sequence. Click Save below after modification, as shown in the figure below;

5. Insert the USB flash drive startup disk, press f 12 repeatedly when restarting, open the quick startup menu, select the identified USB flash drive to start and enter, and start from the USB flash drive to change the mbr hard disk partition. After changing the partition, you can reinstall the system. Be sure to remember that after changing the legacy mode, the hard disk partition format should be changed to mbr, otherwise it will not boot, as shown below;