Some MAY work, often there are some that will not though. If there are no Windows 7 drivers available from the OEM's website, you can try the install and see if windows 7 will automatically find and install suitable drivers, but quite often you'll find that the hardware vendors haven't bothered with backwards compatible drivers since there's no real benefit for them to doing so.
I'd leave windows 8.1 installed anyhow. If the Metro screens and lack of normal desktop function are what you don't like, install Classic Shell which returns the user interface to a Windows 7 style shell with Win7 start menu and desktop function. It's also highly configurable by right clicking on the start button after install and changing it to suit your...