Asus laptop does not boot Linux from USB stick?

I'm desperate. I've been trying to get Linux Mint running on my Asus Eee laptop for a few hours now, which shouldn't be difficult. For this I have booted a USB stick, using the win32disk Manager application. First everything worked out without any problems. Since my laptop only has 32 bits, I only tried it with the last 32 bit version of Linux Mint, that was 19.3 (I've already tried it with the oldest version, 18.0, the problem remains the same…).

Then I went into the BIOS and changed the boot order as follows:

1st Removable Dev.

2nd ATAPI CD-ROM

3rd HDD: PM-ST925…

If I now save and exit, the laptop still starts with Windows. Where is the mistake? On the laptop or on the stick? Unfortunately I have no way to try the stick on another PC. I'm really desperate right now and thank you in advance for any help!

PS: my BIOS battery is completely empty, but for a short time it should save the settings, which I also see in terms of date and time.

PSS: Windows 7 is preinstalled on my laptop. I would like to run Windows and Linux in parallel, but if there's no other way, I would also be willing to delete Windows completely.

I would check the stick again. Rufus is a good free program for creating bootable USB sticks.

Maybe that helps.