I have someone's old computer that i have restored back to factor settings. 2009 Windows Home Premium, 64-bit, Intel core 2 Duo T6600 at 2.2Ghz. 4GB ram. But does not play youtube and other internet video. It does not show signs that Adobe Flash Player or other software is installed on the system. Figured I would start with the Flash Player and go from there, but want to make sure I download the right version for this older system.
As long as you have a supported operating system (see Adobe Flash Player | Tech specs) your system has plenty of memory for Flash Player. As for the processor speed, it should be fine unless you're performing heavy gaming or something similar.
You can download Flash Player at https://get.adobe.com/flashplayer. The page detects the operating system and browser and offers the Flash Player version for that browser. If you use multiple browsers you'll want to repeat for the various browsers.