Best way to Convert MP3 to correct sample rate?

[Carlton_Bale]

Long ago, before I switched to FLAC, I ripped a bunch of albums to MP3.  All of the "important" albums have been re-ripped as FLAC, but I still have a bunch of mp3s that I don't want to re-rip.  Unfortunately, I somehow ripped them using an unsupported sample rate.  I know that the supported sample rates are 11, 22, and 44.1 KHz.  

My question is, what is the best method of converting files to a different sample rate?  I know that I can re-encode them but I really don't want the music to go through two stages of compression.  Is there some way to up-sample to a supported sample rate without performing a decompression / recompression on the files?

Thanks in advance for any help.

[Carlton_Bale]

Now that I've looked at the files more closely, it appears that they really are 44.1 kHz.  For some reason, PNMM reports them as 8000, 32000, 48000, etc.  But when I look at the file in FooBar2000, it is 44100.  Why won't PNMM display the correct sample rate?  I deleted the database and started over with the same result after the scan. . .