My recommendation would depend on what kind of filters and effects you're going for. If you just want basic photo manipulation, management, and effects such as sepia, tints, etc. I'd say go with Google Picasa. If, however, you're wanting to do advanced edits to your pictures, I'd highly recommend Paint.NET. One thing to keep in mind is that not all image editors/managers are the same or have the same purpose, with that thought in mind, it may not be a bad idea to download a couple different ones and give them a try, if you like it, keep it, if not, try another. I'd recommend you start with the above two and make your way from there.
Hope that helps!