title says it all.
unless there’s another program that’ll show ALL the posts to a newsgroup.
Go to Google Advanced Groups Search, type in the name of the group, and it’ll return a listing. Or did you mean something else?
Another possible problem, and I am not familiar with Google newsgroups as my ISP carries usenet, is that not all of the individual posts to a particular group may actually be there. An ISP, or Google, may not have them all due to synchronization issues. An individual who uploaded a multi-part post (large images, multimedia files, etc.) may not have successfully gotten all the posts uploaded successfully, etc.