Hello,
It looks like you are trying to go back to windows 7 form chromium.
If that is true then the following steps will help guide you:
If you still have the product key (usually on the bottom of the device) then you can download an ISO of Windows 7 from the Microsoft site:
Else if you don't have the key then I would recommend downloading windows 10 instead:
After you have downloaded the ISO you will need to change the name to windows10.bin MAKE SURE IT ENDS IN .bin AND NOT .iso else it won't work.
Now you will need an imaging software to burn it onto a USB, I recommend using the "Chromebook recovery tool"
Open the app and click on the settings icon (top right) and then select "use local image", then open the file you downloaded earlier on, and follow the steps provided on the software.
Please note this will erase the USBs contents (deletes everything on there)
After that has compleated you will be able to boot your USB and install windows.
If you would like to still use ChromeOS then I recommend downloading a VM image of chromiumos.
I hoped these instructions helped you If you are having any problems with them feel free to ask.
Adam.