Try the 3.0 alpha of Paint.net; I've heard good things about it.

I wouldn't suggest giving up on GIMP, it can be pretty difficult just to figure out how to install it xD

But paint.net http://www.getpaint.net/download.html You'll have to download the .NET framework if you haven't done that, so you may wish to choose the 40mb download instead of the 3mb ones.

Also, win-zip is nothing that should be paid for. If you use windowsxp, you already have an unzipping utility built into your computer. If you don't, you can download winrar, which handles more files, and while it is demoware, won't hinder you any, just gives a nag screen.