I have been using TopWinMovieMaker for over 3 years now. Yes, you do pay to take if you don't want the watermark, but it is a one off payment and that's it so you can make as many films as you want, ie 1 - 100+. Their support has always been good and there are many features to use, that are being updated. I have made many videos which include stills and video clips in the same film.
I was a total novice at the beginning, but through trial and error, was so pleased with my first one (with watermark), I paid the one off price. If it had not been any good, I would not have bothered but, it spurred me on to make more. Over the 3 years, I have become more and more advanced, mainly due to the ease of the system.
I think Movato is the other one, this also charges for no watermark and probably works the same as TopWin.
If you want a one off film, perhaps Windows Movie is the one to use, I didn't like it myself and I don't know if it still exists. To be fair, I googled Windows Movie Maker and I thought I had it, but didn't realise it was Topwin, but I can't fault them..