I recently found a very basic free online photo editing tool that works well for making banners. It does not need to be downloaded onto your computer, you don't need to make an account or give any contact info, and at the end, it saves your image onto your computer, not to any online site.
http://pixlr.com/express/
1. Click Browse, and find the picture on your computer.
2. Click on Adjustment, and a long bar will pop up along the bottom of the picture with options.
3. Click on Resize, and make the width 1500. Click on the check mark to apply.
4. Click on Crop. Use the little squares in the corners to slide the crop bars up and down, until the height in the box at the bottom is 150. If you can't get it to stop at exactly 150, don't stress. Get it as close as you can (slightly too big is better than slightly too small. ie, choose 151, rather than 149), and click the check mark again to apply the crop.
5. If your height is not exactly 150, go back to Resize. Enter 150 in the height. It doesn't matter if the width isn't exactly 1500 (it can be any width, as long as it is wider than 1200), but the height MUST be exactly 150.
6. Click the Save box in the upper right. Enter a name that will be easy to remember (I include the word banner in each one), and slide the Image Quality up to the maximum. Click the check mark, and then select what folder you want to save it in on your computer. Personally, I have a folder called My Pictures, and within that I have a folder called Gardening. Inside that folder is another folder called Banners. That way, all of my banners are in one place, and I can locate them easily.
Hope this helps someone get started, even if you don't have Windows Picture Manager on your computer!
Angie
I found it when I was helping someone else who didn't have Microsoft Picture Manager, and was ready to pull her hair out trying to do it in Paint. I used to use Picnik online, but they've closed down.
You haven't? 
