Holdkey is available for Windows 7,8,10 xp and Vista.
If you install version 3.5 you will probably see the Microsoft Defender Smartscreen. See images below
You need to click 'more info' and 'run anyway' to install version 3.5
It is absolutely safe but it takes some time by Microsoft to remove this warning.
Version 3.4 already passed this issue, so if you prefer you can download version 3.4 HERE
Holdkey version 3.5 PRO