Hi Reggie,
What software did you use before? Did you want to switch it back so you can open the file with the old program (assuming its still on your computer)?

Here's how to do it in Windows XP:

If you select the picture file (in Explorer) and right click, it should give you a drop down menu.

Click "Open With" and there should be another menu

Click "Choose Program" then a box should appear.

You should be able to see a recommended listing of all software that can open your file. Select the software and also click the box "always use the selected program to open this kind of file". Then everytime you double click the file, it will open with that program.

Note, you may have to do it separately for all diffent file extensions/formats (example is JPG and BMP). Hope this helps.
Greg