For what you are describing I think Bridge would work better. It will be more of a pure browser than Lightroom and if you aren't going to use any of the other modules then you might as well go with the slimmer program. However, LR can index your current file structure, so if you want to you LR you shouldn't have to make new libraries.
Also, I'd recommend taking a look at Camera Bits Photo Mechanic as well, it does what bridge does but I find it to be a much faster, much more reliable approach. I love Photoshop CS3, however, I have had nothing but pain and heartache with Bridge; I find it totally reliable and slow to boot, even on modern systems. If you are big on keywording and other metadata, Photo Mechanic has one of the nicest ingest features I've ever seen.