Install CentOS 7 using text mode
CentOS 7 has an option to install in text mode.
When you see
install centos menu option press the tab key, add
text to the end of any existing installer command line arguments and then press the return key.
This will tell the installer (Anaconda) to install the OS in text mode.
In case you are directly connected to the console of your headless system, just add
to the above mentioned boot command. This will redirect the output to the serial console (bear in mind, that 115200 is the console speed). So the complete line would be
linux text console=ttyS0,57600n8
for a console output with a speed of 57600 baud.
It must be the same speed as it is configured in your Putty session under serial speed. In case you are connecting to the console from a unix-like-system (Linux, BSD, OS X) it can be done with screen:
screen /dev/ttyS0 115200,cs8