When you try to download a Modpack and there is a error like this pls follow this steps!

Press the Windows button and go to the settings!
Now navigate to the apps!
After that click on the search bar.
Type in “Java” and press on the Java “8” / “7” field.
Now uninstall the selected Java version.
Now do this with all your Java versions! Download the latest Java version! Download Page 64 bit version
Now open the java.exe file and install it

Now try to install the modpack!