Google groups are Usenet. A site called DejaNews used to index the content of all non-binary newsgroups. Google bought them and made the service interactive.
That said, from the information in the other thread, you want access to binary newsgroups, to which Google does not provide access.
That means you need a standalone newsreader (or, if you’re a masochist, the Outlook newsreader). You may or may not have to pay money to access Usenet. Many ISPs have their own news server or a contract with a major news provider that allows the ISP’s clients access to the service for free.
You’ll have to check your ISP’s website to find out the address for their NNTP server. Often, this is buried deep within their and you really have to dig for it. If this doesn’t work, call them and ask if they maintain a news server.
If they don’t, you’ll have to pay. For binary news services that have long article rentention, expect to pay about $10/month for 6GB of downloads… Some with shorter rentention times offer unlimited downloads for $15-20/month, but those companies usually provide spotty service and a lot of incomplete binaries. Generally, if you’re using your ISP’s free server, this is what it will be like. Some ISPs are even worse in that they have poor service, low retention, missing posts, and a download cap. There are also ISP’s that filter out popular binary groups for various reasons.
If you’re just looking for one specific file and don’t want to pay a monthly fee for something you won’t be using in the future, I’d recommend the Teranews “free” service. It’s a one-time fee of $4, and you get 50MB/day for downloads and unlimited uploads forever.
Also note that “subscribing” to a newsgroup is much more like a bookmark for a web site than a subscription to a magazine. Since there are tens of thousands of groups, you subscribe to a few that you like so you don’t have to scroll through that huge list to find them again. Nobody on the newsgroup knows that you have subscribed. Like a bookmark, the subscription setting is entirely local to your computer.
See here for some guides to using the newsgroups. For a news reader, I’d recommend the freeware Xnews.