is nero mp4 he-aac in foobar only convert one file, how to convert more files in same times ? is cmd line is following nero he-aac ? And btw tell me example that cmd line ?

no

you don't really need to use a command-line to use HE-AAC. foobar2000's converter plugin has a nice GUI for everything. as for the encoder itself, it encodes 1 file at a time. but foobar2000's converter plugin launches 2 nero encoders at the same time.

if you want to convert more than 1 track, just select all of them and right click Convert.

It launches one for each "CPU" that you have.

when i convert files, the running progress so slowly, so far from nero 7. And didnt convert under 16 kbps, when try 10 kbps, the msg is error cmd line. Why winamp can reach 10-8 kbps with 32khz, but only ripping?

Is it possible for fb2k to only convert one file at a time instead of two?

Yes. Using the Windows Task Manager, you need to set the affinity of the process "foobar2000.exe" to CPU 0. To do this, open the windows task manager, click on the processes tab, right click on foobar2000.exe, select "Set Affinity" and uncheck everything but CPU 0. This needs to be done each time you launch foobar2000.