How to make a program auto start in win8PE

I've a program say abc.exe , and want to auto start to run this program when win8pe boot up.

Something I found very strange. When I mount C:\Win8PE_SE_2013-10-03\ISO\WIM\sources\boot.wim to C:\mount , I found some files in C:\mount\windows\system32 , they are :

     winpeshl.ini , startnet.cmd , start.cmd

I know I can place the abc.exe in one of them and can be autorun. But when I boot up the win8pe , all the above 3 files are disappear.

In the mounted C:\mount\windows\system32 , the 3 files do exist. How come when boot win8pe , they disappear ?

So I can't find a way to place the abc.exe to autorun.

Please help