If you say what you want to do then I can probably recommend a free piece of software.
IrfanView is mostly a picture viewer but can do some editing.
The Gimp (ignore the name) is a very powerful image editor.
There are many others, it's rare you need to pay for anything us geeks might be interested in as it's probably already out there for free.
Lastly, does your camera not have software with it?