My three years old self built system still runs New Vegas on high settings and 1920x1080 resolution quite nicely (most of the time > 30fps).
Core2Duo E4700 (2x2.6 GHz)
4GB DDR2 800 RAM
GeForce 9600GT 512MB (MSI's factory overclocked model)
Cost me some 500€ back then (that included no case, no OS and only 2GB memory).
And the ye olde family desktop runs it too:
Celeron D 2.8GHz
2GB DDR 300 RAM (or something, can't remeber)
Radeon x1550 256MB
Low settings, 800x600 resolution, terrible framerate, but it runs

Though the chargen gets stuck, have to use a save outside of the Docs house :shrug: