I want to convert some mp3 files to midi but I need to change them to wav first. The program I want to use (Digital Ear) needs the files to be 44100 Hz and it records in foobar at 22500 Hz. Does anyone know how I can change this? Thanks.

Maybe your files are encoded in mp3 pro?
If you want to convert them to 44100hz go to the diskwriter settings and enable option under processing section: use DSP.
Then in DSP settings enable resampler and set it to 44100.
Now your files should be converted to 44100hz.