windows-xp – Why Does Windows Explorer Connect to Port 80 Instead of SMB?

Background:

On an almost freshly installed pc I get a message along the lines of : "windows cannot find some-file-server-name. Check the spelling and try again"… when trying to access any fileshare.

Troubleshooting so far:

• pinging works. Both by ip and by name
• the almost identical pc next to this one can access the file server
• everyone else can access the file server
• the pc in question can not access other open fileshares
• but it can connect to the internet

And now for what I think is the interesting part:

• running wireshark with ip.addr == local.ip.add.ress and ip.addr == server.ip.add.ress tells me that it tries to connect over http.
• the server replies but after a few messages back and forth it stops
• the other machine of course just uses smb

I guess port 80 just means it defaults to webdav, but I haven't been able to find anything that can cause this.

Googling it the closest thing I found was this http://www.techrepublic.com/article/get-vista-and-samba-to-work/6353849 but then again this was an XP pc and I wasn't able to connect to other native Windows shares (and I tried the solution anyway and it didn't work.)