If you read through
this, thread you will see various Vista possibilities.
Try... C:\Documents and Settings\My Name\AppData\Roaming\Marine Aquarium 3 .....
or something like that!
Better still, search for a...
'Marine Aquarium 3' folder, and place AltLogo.png in it. .....
Or get rid of Vista! 
Edit: Not sure how much it will matter, but the file we are replacing with our own logo, is called AltLogo... not Altlogo.