Since the game was released in 2004, most modern lag issues stem from the game not knowing how to handle modern hardware (multi-core CPUs, high refresh rates, and new graphics APIs).
The Problem: Modern multi-core processors often confuse NFSU2, leading to stuttering or "hitchy" frame rates even on beastly PCs.
Need for Speed: Underground 2 remains a classic, but playing a game from 2004 on modern hardware like Windows 10 or 11 often leads to frustrating lag, stuttering, and low frame rates. Modern systems are more than powerful enough for the game, yet software incompatibilities and multicore processing issues often cause it to run poorly.
Try reducing the graphics settings to a lower level: