I've searched, and found nothing. Sorry if this is a repost
Go to the desktop, and hold the windows logo on you keyboard down, and press R.
Write "regedit" in the box, and press "OK"
When you've done with that, the program "Registreringseditor" (Translated to English: Registrationeditor) should open.
Now hold CTRL and press B. A search box should open now. Enter that program you want to delete the registration files from, and press "Find Næste" (Translated to English: Find Next)
Now delete the folder that the search found by pressing the "Del(ete)" button on the keyboard.
Repeat this until theres no registration files left of the trial program, and then you're done
And again... Sorry if this is a repost. And sorry for the big screenshots >.<