Experimenting with creating a web banner

Today I have spent my public holiday day off playing around on the computer trying to learn how to create banners and buttons without using Photoshop (which I don't have, and can't afford).

I created a couple of banners easily enough in Microsoft PowerPoint, and was more than happy with my beginner design efforts, but do not know how to resolve the issue of removing white space that appears around the banners when I attempted to upload the banner to Blogger. That white space wasn't there before I uploaded, I haven't gone outside the banner edges, so I don't understand why it is there after I upload.  As I learned very quickly today, as much as I love using technology, I am at a significant loss when it comes to anything away from word-processing - sigh.

What do you think of my first banner-creating effort?

I'm developing a growing interest in creating web banners and buttons etc.  Do you know of any good free or cheap programs that are easy to use, and any great websites or blogs I can visit?  (My son had Photoshop a few years ago, but I found it way too confusing to use).