"This only seemed to have started since swapping to a new wireless router (and switching to PPTP from PPPOE)."
"The thing is, the laptop does auto connect to the router"
The above tells me that it is your router & not your PC that is at fault, however you can try to remove miniport's by:
Boot into safe mode
Right click on the miniport, choose “Update Driver”.
Choose “Browse my computer”.
In the next window, choose “Let me pick driver from a list”.
Uncheck “Show compatible hardware”.
From the “Manufacturer” list, choose “Microsoft”,
From the “Network Adapter” list, choose “MAC Bridge Miniport”. (It can be any device the user is allowed to uninstall.****
In "Device manager", delete the device that just turned into the “MAC Bridge Miniport” device.
Once the miniports are removed, reboot.
The only thing that mitigates against that is that I have tried 4 other wireless devices on the same router, starting with them all off, and turning them on in different sequences, and the only one that has a problem is the same notebook laptop, all the other
devices autoconnect with internet access, regardless of whether there are other devices already affiliated to the router or not.
When the troublesome notebook is connected to the router, but has no Internet access, if I check the adapter properties, it has a totally random IP address, well outside the settings in the router, so despite being set to have its IP address dynamically
allocated, it seems to get one from elsewhere, or makes its own up.
Is it possible that the notebook is possessed by the devil - and needs an exorcist?
I'll give the other settings a try as well
Thank you for being patient with this, maybe we'll get an academy award when we find out what the problem is.