Question: We have recently moved to a new ISP and my Windows 8.1 ThinkPad will not reliably connect to the new network. I am not having issues with any other devices, but this laptop barely works at all. 

It always connects, and sometimes works extremely briefly, loading, say, half a Web page before giving up. Sometimes Windows claims limited connectivity, sometimes it claims to have Internet connectivity when it does not. 

I have tried removing the network (even from the registry) to no avail. 

I'm not sure where to go from here, suggestions appreciated!

Answer: 
I would

1. Try using the laptop as close as possible to the access point to see if there is some source of noise disturbing the communication
2. Load a [linux live-CD](http://www.knoppix.org/) (works out of the box on my thinkpad) onto USB stick and try using WiFi. If it works well, the problem may have to something with windows.
3. Change some parameters like WiFi channel etc.

edit:
4. Maybe you have some WiFi stick around, then you can try that one instead of the build-in card.
Whenever troubleshooting wireless issues, always try to determine if the issue is local to your network or with the device itself. The easiest test is to take the device to a local hot spot (public wi-fi, such as "Starbucks" or even "McDonalds" and test your connectivity.

If you are still having issues, then concentrate your efforts on the device itself (upgrading the O/S, component drivers, etc.)

If there are no issues, this is where you need to look at what's happening with your access device at work. It may need a firmware or software upgrade (have you tried rebooting the device?).

If still having issues, purchase a USB wireless device. Disable the on-board wi-fi and install the USB wi-fi and see if that does the trick.