Ok so I'm not very knowledgeable when it comes to to modems and routers. From what I understand the DPC 3825 should act as a modem and a router unless it's been bridged, which it has not. But for some reason if I unplug the router that's connected to it, the E1500, the Wi-Fi disappears. So my question is, do I need the router or no? Since clearly the DPC 3825 isn't working how it's supposed to. Also I have 2 Wi-Fis in my house. One for the DPC and one for the E1500. I don't really get how this works.
SO ALL IN ALL... How do I get the DPC working without the extra router?
Like you said, you are seeing 2 wifi's currently, with your the E1500 plugged in. One wifi, would be from the E1500, and one from the dcp.
Youe wireless devices that are connected to the e1500 wireless, when you unplug it, will loose their wireless, as they are not set up to connect to the wireless on the DCP3825.
Now, if you unplug the e1500, the only wireless left should be the one from the DCP. Now, if this was never set up properly, this will need to be done. You would have to network cable plug into it, to do this setup. The address to set it up, should be 192.168.0.1 or 192.168.1.1. (put this in a web browser address bar) Now, the login for it.. not sure if default or was changed, ,etc.... All in all for this.. might be best to call rogers.. they can help reset the device, so back at default login/password, and can probably even help you set up the wireless settings from there as well.
Now, the question you brought up "Do i need the router or no?" Most people here, would say YES. Only for the reason, that while the DCP has wireless built in.. it is not very good. You will get MUCh better wireless performance and range from the E1500.
You could keep your current config, but it does keep the other wireless on (also on the DCP for some reason, even if you DISABLE the wireless. it seems to turn back on). Other option, as you said, would be bridged mode.