Windows Defender anti-virus or not?

In my extreme hopes I looked forward to a release from MS for virus and other attacks on the operating system.

Ergo, the moment ‘Defender’ was released I installed it.

While ‘waking up’ a laptop running a 4 year old version of XP Pro with a very annoying Adware message that the register was in need of repair. Only PCTools virus program was able to rid the ‘nasty’ virus.

It also registered itself as an ‘anti-virus’ program within the firewall.

Surprisingly ‘Defender’ does not register as such; although I’ve had no attacks on my system.

What gives? Is MS so ashamed of it’s own ability?

Is it anti-viral or not?

As of the moment I use it (stupidly?) as my only protection.