Dell Inspiron 3584

You need to install a supported operating system -- this model uses a 7th generation CPU, for which Windows 7 is not supported.

You need Windows 10 or 11 to work with this model.

There may be ways to get Windows 7 to run, but that OS is dead and buried -- it is completely insecure and unsupported since January 2020.

As ejn63 wrote, Windows 7 is unsupported and insecure. It does not receive security patches, so it should no longer be used on a PC connected to the Internet.

You can do a free upgrade to Windows 10, using your Windows 7 Product Key.

Your old application will likely work in Windows 10 if you install it and/or run it in Compatibility Mode. I've found that most old software I've tried will work with Windows 10 in Compatibility Mode.

Alternatively, you need an update to whatever software you have that won't run under Windows 10, or you need a system that's a generation older (the 6th generation of Intel CPUs was the last that will run Windows 7).

If you're using this online for business purposes, you should also consult your insurance carrier as well, as it is very likely that they won't cover you against losses incurred by running an application under Windows 7.

Yeah, but I have a software that only works on Windows 7, oddly enough it is not compatible with Windows 10, and when installing Windows 7 I had no problems. It just doesn't start the system, it doesn't recognize the HD.