No detected operating system

[JesseVoss]

Hello,

This is my first time trying to install Linux Mint. I have an Acer Aspire E 15. I got into BIOS and went into legacy mode for boot because it wouldn't allow me to use USB boot otherwise. Linux Mint started up and I went to install it. When I get to installation type, it says there is no operating system detected even though I have Windows. I'm trying to do a dual boot and I don't want to erase everything on my computer. But it's only giving me the option to erase disk and some other ones I don't understand. I've tried getting back to BIOS but it now only automatically boots up with Linux Mint. If I don't have my USB in, it shows me errors and I have to restart with the USB so I can at least get it to show something. If I can't download Linux without erasing everything, I at least want to get back to Windows so I can use all my programs.

Any help will be apprecited.

I didn't find the right solution from the Internet.

References:
https://forums.linuxmint.com/viewtopic.php?t=271632
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Thank you.