The game is not currently sold on Steam, EA App, or GOG due to expired car and music licenses.
Millions of combinations for parts like spoilers, rims, and neon.
If downloading from archive sites, always use a reputable antivirus to scan the files first.
Second-hand discs (eBay/Amazon) are the most legitimate way to own it.
You will likely need the "NFS Underground Widescreen Fix" to run it on Windows 10 or 11.