There's a Moo, Moo, Moo, floating text, in your screen. My guess is You've probably messed up your Nevada installation.
You see, the installation file asks to provide it with fallout folder, but it should install in a subfolder inside the "Fallout 2" folder. This is most porbably due to installig both games in C:\Program Files\ or C:\Program Files(x86)\
those directories are default installation folder for most programs, however, they're a no-no for classic Fallout games.
You see 'Fallout' and 'Falout 2' were originally released waaay back when windows did not secure C:\Program Files folder from program and user acces. However since at least windows Vista "Program Files" and "Program Files(x86)" are guarded by windows, and prevent certain 'stunts' some of the Fallout mods do, such as High Resolution Patch (known as HRP or f2-res.dll) or Sfall (placed in ddraw.dll). so in order for Sfall and HRP to work correctly you must reinstall the game to a different folder such as C:\Games or D:\<whatever> just *not* into "Program Files" or "Program Files(x86)"