I still have some things which I'm unsure off (as I don't know how to do so).
About not being able to connect;If that resolves it, then just point your DNS to the googles, and not your ISPs. And file a complaint against your ISP for filtering your DNS(if that is what is happening to you).
Sorry but, how do you do that?
IIRC, from what you posted above, your DNS already finds dpmaster, so you shouldn't need to change it. Anyway, you may refer to this:
http://www.computerhope.com/issues/ch001161.htm
How do I open or change ipv4 actually?
In Windows XP, in your local network properties, if you see "Internet protocol (TCP/IP)", it's referring to IPv4. IPv6 support in Windows XP was only optional (experimental?) and you had to install it manually. In later versions of Windows, you should see a line mentioning IPv4 and one mentioning IPv6... you chan check or uncheck them to enable or disable that protocol for that network card.
See also:
http://www.oit.umass.edu/support/ethernet/check-your-computers-tcpip-settings
After testing OA with firewall-settings of the router off, it did succeeded this time.
This is very interesting. Please do more tests in this direction. I don't know exactly what to think... maybe trying to enable the firewall, but disabling those DoS protections?
Anyway, if you use NAT (multiple PCs behind the router share the same external IP address), you may even disable router's firewall at all (keeping active the Windows one if you wish)... a NAT by itself protects from externals attacks (unless in ports where you configured a virtual server or similar)... be aware that, of course, the NAT by itselsf would does
not block malware you got in other ways to later contact external servers...
I noticed when I start up OA and search for servers, my desktop suddenly says that it has no connection to the internet at all (if I switch from OA back to the desktop interface).
Maybe this causes it? Any ideas how to solve it?
I don't know....
About OAWire;
After a successful installation you will have the OpenArena logo in the bottom right corner. You can activate the menu with left clicking the icon.
I don't see anything appear at all after installing it correctly? Next to that, are they talking about some logo within the screen of my browser or just in the taskbar?
In recent Firefox releases, you have to enable the "Addons bar", because it's hidden by default. From "Show/View" -> "Toolbars"-> "Addons Toolbar" (I don't know the exact names used in English version of Firefox, due to mine being in Italian). You can also show/hide it by pressing
Ctrl+/ (the slash on the numeric keypad).
OAWire author should update the addon description to mention this.