Plugins disseapearing from one account ?

[Aethec]

Yesterday, my little brother asked me to use Paint.NET. So I pressed Windows+L to change from my account to his, and started Paint.NET...I was showing him the Effects menu, when I noticed something :

In my account, when I use Paint.NET, I have 5 effects in the Effects submenu : Align Object, Erode/Dilate, Alpha Diplacement, Custom Brushes and Flip (the original, not the two "flip horizontal and "flip vertical", I don't like having a too big Effects menu)

But in his account, he only has Custom Brushes and Alpha displacement..3 effects missing...We are using the same computer, Paint.NET is installed in the default Program Files location, ...How is this possible ? I verified two minutes ago, the DLLs are in the correct directory..