It is important to understand the legal context surrounding game backups and emulation. Generally, digital preservation and copyright laws stipulate that downloading an ISO file from the internet falls into a legal gray area.
Once you have acquired your legally sourced copy of the Need for Speed: Underground 2 ISO, you have two primary methods to play it: Method 1: PC and Mobile Emulation (Dolphin)
Released in 2004, Need for Speed: Underground 2 is an action-packed racing game developed by EA Black Box and published by Electronic Arts (EA). It's the sequel to Need for Speed: Underground and continues the story of the original game's protagonist.
By default, Dolphin will emulate a standard GameCube controller. To set up your controls:
This is the most critical section. While emulators like Dolphin are legal, downloading copyrighted game files (ROMs or ISOs) from the internet without owning the original game is, in almost all jurisdictions, a violation of copyright law.
While the original question asks for a GameCube ISO specifically, it's worth noting that Need for Speed: Underground 2 was also released for Windows PC. If you don't own a GameCube disc but still want to play the game, obtaining a used physical copy of the PC version is often the most straightforward path. Once you have the PC disc (or an ISO of your own disc), you can install and run it natively on modern Windows systems, often with fan-made patches and widescreen fixes that improve the experience beyond what the original console versions offered.
If you prefer the authentic feel of retro hardware, you can load the ISO onto a homebrew-enabled console: