I've installed Windows 10 on HP EliteBook 2730p from 2008, and Toshiba Protege M400 from 2006. For the most part if the machine ran Windows Vista acceptably it will run Windows 10. Disk access is pretty slow. Windows 10 really needs an SSD.
Additionally, on extremely underpowered CPUs, you realistically need to turn off Windows Defender's real-time virus scanner in order for the machine to be usable.
I got an 11" Dell Inspiron with a puny A6-9220e (1.7ghz, 2 core) CPU that is roughly comparable to an Atom, but with a somewhat better GPU. Replaced the HDD with a SATA SSD. Thought it would be a cute little beater netbook.
For all intents and purposes, it's just not usable unless that real-time protection is turned off. Things freeze up for multiple seconds while clicking any button, apps take dozens of seconds to launch, etc. With real-time protection off, it's pretty decent - good enough for web, YouTube, iTunes, Spotify, whatever.
Unfortunately, Windows turns real-time protection back on automatically after a certain amount of time. Apparently you need Win 10 Professional or higher to permanently disable it via group policy or something.
