It's not the program's fault it's slow, it is probably the settings you are using.

I use LAME 3.97 Beta 2 with --alt-preset Fast Extreme and VBR 2. Then I adjust the bitrate max and min to whatever the source dictates.

The rest is CPU power. I have an Athlon 64 3200+ (Venice) and it can do a full CD in about 5 minutes. And that's with copying the CD audio to the hard drive first as WAV and then converting. Ram is 1 GB dual channel