I dont know how the infranview works.
But try this (I´m not sure if this works on infranview):
1. Turn the image to B&W
2. Blur the image alittle
3. Add noise (Just alittle bit)
4. Blur again to blend the noise to the picture
5. Make new layer and paint some scratshes and dust to it
6. blur the scratshes
I dont use this method anymore, but as you dont have photoshop, my current method wont work.
And here´s the aged photo:
