Question about Outlook Express

When I turned on my WinXP tonight I noticed that the MSE icon at bottom of screen was now "YELLOW" instead of the usual "GREEN." When I opened the MSE, it too had "YELLOW" border and 'warning' about MSE being discontinue for WinXP.

#1- Is my MSE still protecting my WinXP System, even though it is now colored "YELLOW?"

#2- How will I know when it is NOT protecting my WinXP System?

I have Win 7 and MSE and I'm satisfied with it as my AntiVirus. (also have a  few antimalwares).

In my son's new computer there is Win 8. In the beginning he had Free Norton AntiVirus.

Now that it will expire I wanted to suggest he downloads MSE, but I am confused because I read that you can't get it with Win 8.

I only have one day so it is a little urgent.

I read that you can get Win Defender instead, but it's not an antivirus.

1.Is there any way to install MSE in hiswin 8 computer now?

Please instruct me about it.

2.  I guess I should uninstall Norton first, and I remember uninstalling isn't enough, pls instruct me what to do...

3. And while having Norton uninstalled and no other Antivirus yet you are really vulnerable in the ,meantime. isn't it?

4. I remember in the past I installed the Defender on my computer, but I uninstalled it because it would constantly ask me

if the programs/processes running are good or no. If I allow thaem or not.

But I wasn't able to know if a name was a malware or a process coming from a legal source.

And you can't work having to approve all the time...

5. So what should I do now with his computer if I dont want to pay for an Antivirus.

( In the past the forum recommended me MSE as antivirus + security free and good software)