The original game only supports 4:3 resolutions. Download the NFS Underground 2 Widescreen Fix (by ThirteenAG) to allow for 1080p or 4K resolutions. Compatibility Mode: Right-click the speed2.exe . Go to Properties > Compatibility .
Check out community-made "Reshades" and texture packs (like the NFS Underground 2 HD Reflections mod) to make the game look surprisingly modern. need-for-speed-underground-2-pc-download-ocean-of-games
Sites like MyAbandonware are generally considered more curated and community-vetted for old titles that are no longer for sale digitally [2]. The original game only supports 4:3 resolutions