so i decided to buy fallout 3 on here rather than steam. The game starts fine but as soon as I start a new game, the game freezes and then closes itself. I downloaded the d3d9.dll file but soon I couldn't even start the game without it crashing again but this time I didn't even get to the main menu screen. It immediately freezes and crashes. anyone else have this problem as well?

Have you used the unofficial patch? theres some good stuff on the internet. I use the fallot mod mgr also.

Downloading the d3d9.dll alone won't do anything if you haven't installed the directx files it links to. I'd suggest this first:
https://www.microsoft.com/en-us/download/details.aspx?id=19743

And if that first one doesn't do it see if this specific directx 9 one works:
https://www.microsoft.com/en-gb/download/details.aspx?id=34429

Basically these are Microsoft installers that look for and add any missing directx files. There's a Lifewire page that explains what they are, what they do and what you're supposed to do with them:
https://www.lifewire.com/how-to-download-install-directx-2624489

Hope that this is the issue and that it solves your problem.