Reinstall on different computers

[REDACTED]

I bought and installed Avast before I realized that using windows 8.1 it was not needed. I uninstalled all but the sandbox (I think). Anyway, I am about to add 2 more computers to my network. Older machines that I have brought up to date. One an XP and one
 with Vista. Since my account is still open I want to run Avast on the extra machines. Do I just bring the new machines on-line, go to the Avast site and type my code for downloads?

[Eddy]

On Windows 8.1 you also need a good av for protection.
The MS one is not good enough.

If you want to protect 3 systems, you will need a license for 3 systems or 3 separate licenses.

[Para-Noid]

You may want to read this http://www.howtogeek.com/173291/goodbye-microsoft-security-essentials-microsoft-now-recommends-you-use-a-third-party-antivirus/