Hi, Glenda. I am a member here but manage other MSN sites.
I can't tell you how MSN sites will interact with yourcomputer if you run something other than a Windows operating system in your computer, but I can give you a few tips about using the groups in general.
To reply to a message, the easiest way is from the message board itself (not from your personal e-mail, even if you get a daily or weekly digest). Just click on "reply" and a pop-up tiny window will form. Type your reply in there. (You need to be signed into the group of course.)
You can click on "reply" in any post within a message thread and it'll work fine.
Can't help with the chat question except to tell you the MSN groups did have chat rooms prior to Oct. 18, 2006, when they all went away because they could not be monitored and surveilled by authorities interested in such things. I think this group does have chatroom arrangements outside of its own site, on another secure server but I don't attend chat here, as I am already otherwise obligated elsewhere.
Maybe you were seeing the registration and sign-in for the chat server?
If you have saved photos to your own computer's "my pictures" folder within the "my computer" file, you can attach the photos to your message. Otherwise, MSN Groups allow for photo storage within the groups and you could copy/paste from there if desired.
There are a couple of places you can go for help with MSN groups questions. Try a group called Community Feedback and the one called Web Design. I hope this helps.
I don't know how computer-adept you are, (hopefully better than I was when I came to groups!), so sorry if I'm telling you anything too simple.