I've read the posts at this and the mame.net forums about area51 and I'm just confused. Hope you can help me out.

I have the original area51.chd. I also have the area51tw_diff.chd file.

Am I correct in that you:
(1) apply the tw_diff file to area51 to make area51a.chd?
(2) the pre-mame 82 area51 (original un-diff file) stays named area51.chd?

The reason I ask is that I renamed the original area51.chd to area51a.chd and clrmame tells me it has the wrong checksums. So I'm assume it's the diff file that needs to be area51a.

Thanks for the help.
Bob