Audacity seems let me record at higher rates that my sound card supports
Audacity will let you change your Sample Rate and Bits per Sample to rates higher than what your Sound Card can support. It will record at the highest rate your sound card supports, and then dynamically upsample the audio to the higher rate your selected - without providing any warnings that it did this. This is NOT the approach you should take for any audio submitted to VoxForge. The upsampling and later downsampling for use in Acoustic Models can introduce noise.
Please check your audio card manual to determine the highest Sampling Rate it supports. If you don't have your manual (or lost it, or never received one ...) these other FAQ entries can help you determine your max sampling rate: