Your game must be patched to v1.2. You will also need a cracked exe.
I. Resolution: UniWS
1) If you already launched the game, make sure to set the resolution back to 640x480.
2) Download and run UniWS.
Select Need For Speed Underground 2 in the drop-down list.
Locate the installation folder (where SPEED2.EXE is, typically C:\Program Files\EA Games\Need For Speed Underground 2).
Specify the New Resolution you wish to use and click Patch.
At this point NFSUG2 is Vert- in widescreen and multi-mon resolutions.
II. FOV: Racer_S hack
1) Download and run (link below)
2) Position the sliders according to your aspect ratio (these are rough empirical settings, feel free to refine):
X FOV: 1.25
Y FOV: 0.809
X FOV: 1.34
Y FOV: 0.79
3) Launch the game. Press Numpad * to enable the hack.
The far & near chase cameras are now Hor+. The bumper & bonnet cams would require slightly different settings but should be ok in widescreen. The rear view mirror and HUD are unaffected by the hack and just stretch.
III. NFS Underground 2 Widescreen Fix
It's a plugin, which allows the game to run in widescreen resolution, defined in nfsu2_res.ini, without running any external tools. Exe v1.2 (4 800 512 bytes) is supported. To install, copy content of NFSU2_widescreen_fix.zip in NFS Underground 2 root directory. By default, if the X and Y parameters in nfsu_res.ini equals to 0, the plugin will run the game in your desktop resolution.
More info and feedback at gtaforums topic.