I'll say in advance, I appreciate any and all assistance with this question.

What I need to do is modify the Registry such that when a user attempts to open up a file with a custom extension (let's say .abc), whatever.abc will launch in the application which I have directed it to use. I will be installing this application on the computer.

I am familiar with the required API's to create keys and values and what not, but I am missing pieces. One can test this out by changing the Shell>Open command in HKEY_CLASSES_ROOT for different extensions. You can tell a .txt file to open in Word for example. I am not having trouble adding/modifying keys to the registry, I just need to know what ones and where.

Again, thank you for any help.