Remove/Reset Friend Code in Animal Crossing City Folk rvforest.dat

[Virus]

That looks correct. Before making any changes, can you verify that the checksum at offset 0x20 can be calculated correctly (i.e. does your hex editor produce the same CRC32 that is currently stored at 0x20)? If so, it is possible there is another checksum that requires updating or the game does not like the value you are saving to 0x40.

[Pc_b]

I've been looking at this post awhile, and I'm trying to figure out how this works, what are some of the things I need to understand before I do all of this?