You can, but it'll sound no better than it did originally. It may actually sound worse, as you'll probably get more artifacts. It will, however, take up more space.

Programs that offer the "resampling" feature are designed for downconverting (eg, 128k->64k) of mp3's to fit onto small devices like flash-based walkmans. You're loosing quality there as a tradeoff for fitting more on the device.

Hugo