There are a number of system calls like (system "rm ...") in news.arc and other places. These run shell commands, and most of them only work on a POSIX shell. I'm sorry to say, I'm not sure anyone has ever gone through all these calls and made them portable so that news.arc can run on Windows.
If you use the Anarki master branch, I think a few of those calls have been replaced with more portable code, but not all of them. I've at least been able to get a server started up and showing content before.
I used to use Arc on Windows quite a bit, and I tried the web server a couple of times, but I never really used the web server. Nowadays I still use Windows, but I do a lot of my programming projects inside a Linux Mint VM using VirtualBox. I think running news.arc inside a VM like that would be one of the easier ways to get it working. Of course, learning to set up a VM like that could be a lot to figure out, but at least that's something a lot of people out there have already written up tutorials for.
Another possibility is to look for one of the many Hacker News clones that people have whipped up in other languages. You probably won't get to use Arc that way, but some of those clones may be better architected and better maintained than news.arc.