I heard that there are many fake FXO modules out there in the market. If the price difference is not big enough and if you tend to get a reliable connection for a long period of time, better choose a real one.
I think what ckleea said was an external USB-CDROM instead of turning a USB flash stick into an USB-CDROM.
In fact, if your USB flash stick is not too old, it can be recognized and bootable by the BIOS. What you need to do is to turn the Asterisk software into an image file in .ISO format and copy it into the USB flash stick as it is.