Multiple networks when I would like only one

I'm not a network expert and am getting into some grief on my home network.

I think the basic problem is I have unwittingly set things up in a way that I have multiple networks on the same SSID, when what I want is a single network. I'll try to explain as succinclty as I can:

1. I have a DSL router/modem on the first floor. Its first LAN port is cabled to a Netgear Powerline XAV5001 adapter.
2. Shifting down to our ground floor I have a mediaserver, running on a fresh install of Windows 8 Enterprise. This PC is LAN cabled to a Netgear Powerline XAVB5101 adapter. Also on the ground floor I have a Netgear Powerline XAVN2001 Wireless N-Extender.
3. In the basement I have a Netgear XAV5004 4-port (gigabit) adapter and a second Netgear Powerline XAVN2001 Wireless N-Extender.

The two wireless extenders are 200 Mbps products, whereas the remainder of the gear is 500 Mbps.

My ground floor mediaserver is the heart of my network - it directly feeds music to my stereo via optical out. Over the LAN it is also meant to serve films to my DLNA renderer Blu-ray player in our home theater in the basement (Oppo 105, cabled to the Netgear XAV5004). The main issue for the network is my mediaserver is a headless build so I need to access it from a Win 7 laptop (using Remote Desktop) or an iPad (TeamViewer).

My problem is either my laptop or iPad (both of which are accessing the network through a wireless connection via one of the two Wireless N-Extenders) does not reliably see the mediaserver on the same network. So even when I attach a monitor/keyboard to the mediaserver and determine its IP address to be, say 192.168.1.36 if I then specify this IP address on my laptop and try and connect with Remote Desktop it fails, reporting the IP address is not on the same network.

So it seems to me that somehow my laptops and iPad are operating on a separate network. Some proof of this is that Windows 7 on my laptop has appended a number to the SSID of my network that my mediaserver is showing - so for example my mediaserver is showing it is connected to "network", whereas the laptop is showing it is connected to "network 3".

I suspect part of this relates to some automatic Window behaviour from when the laptops have been plugged and unplugged from the network and some potentially to the fact that my Netgear equipment has changed over the last few years, having begun with the 200 Mbps stuff and then evolved to the 500 Mbps stuff as I have wanted to stream films over my network.

I have seen that there is a "Push and Secure" button on the 500 Mbps Netgear stuff one can depress in order to assure encryption and to "secure" the network. Their installation instructions are quite brief and emphasize the Plug and Play ease of installation so to be honest I am not sure if I depressed this Push and Secure button when I added in the 500 Mbps gear.

Sorry for the length but I wanted to give a clear explanation and I really want to get this network sorted so I can have bullet proof headless access from mobile devices to my mediaserver. For all you network gurus this is probably quite straight forward.

As I think about this I suppose I am leaning towards a complete reinstall of my networking gear, get rid of the old SSID, set up a new SSID, making sure I depress any and all buttons on the network gear ,etc. Although you may see an easier solution. For what its worth, I do not see any reference to a bridge or non-bridge mode for the Wireless N extenders, and I do not think I have anything other than my DSL router/modem carrying out NAT and DHCP duties.

Thanks for your help and direction,

Dave M