First, consider trying another keyboard in case there is some stuck/sticky membranes like Al & Tab.

The next thing occurring to me would be to scan for malware. The best tool for this is AntiMalwareBytes software - download location is in the Virus/Spyware forum.

Get that one out of the way so that we can rule out a trojan that is doing this.

I poorly titled this post. It is not literally "ALT-TABBING," rather, it is just switching windows. So it's not a sticky keyboard.

She has the updated Kaspersky Anti-Virus installed so I suppose that rules out malware.

Thanks. Seems like a toughie to me.

I understand - your original post was perfectly well written from my point of view. But sticky membranes on the Alt & Tab keys could well produce the symptom in the manner you describe. But it was an outside chance worth mentioning.

Kaspersky is good but there are special tools for malware that might otherwise get past Kaspersky. I admit it's unlikely but ..

So, I hope it isn't to much trouble for you to run Anti-Malwarebytes on the PC and/or HijackThis and then post the logs on the forum. The Spyware/Virus forum here will tell you from where to download this special tool set.

Here is the HijackThis log. Good luck figuring it out lol.

Looks absolutely fine to me.

Have you tried installing TWEAKUI. It's a long shot but if you go to the General sub-category and check the box labelled Prevent Apps from Stealing Focus.

Let us know. And although you thought it was random, perhaps there is a pattern - like particular apps stealing the focus.

Grr... I already tried that haha.