well i downloaded the .rar file and i know i need to extract it using a zip program i downloaded zip 7. what do i do after that? like im not that great with this but wanna try the demo out any help would do and would be appreciated

like a step by step would totally help

If you have 7-zip, then right click on the file, select open with and chose standard application or something (I've got a Norwegian OS, so I'm just roughly translating), choose browse, navigate to the 7-zip folder (usually under program files), then select 7zfm.exe, and use it to extract it somewhere.

i extracted the files and theres the tech demo logo for fallout 3 and opens in a black window and says failed to create d3ddevice

Sorry, misunderstood what you wrote. Unfortunately I haven't tried it myself, so I can't help you, but considering that it's a pre-alpha tech demo, it might not work on every system, and I have no idea of how it responds to different operating systems.