WiFi stopped working randomly on custom PC

It's a Linksys WUSB6300

Did you try installing "Linksys Connect" software?

Yeah I have always had that installed.

Running out of ideas here :)

Do you have another wifi adapter you can plug in to see if it still does this OR assuming your modem has Ethernet ports on the back - an Ethernet cable you can plug to a NIC on your computer? This way we can rule out any high-level protocol issues.

I moved the PC to my living room where the modem is located. Internet runs very fast via Ethernet cable. 60mbps solid.

You said you have 3 adapters - the Tp-Link, panda and linksys. Did you try the previous steps with all of them or just with the linksys? And by previous steps, I mean mainly uninstalling all drivers and software and trying with just the windows default drivers?

Yes, every time I do, it says Windows cannot find a driver.

Have you run Troubleshooting?

Control Panel > Troubleshooting > View All (on top left side) > Network Adapter

Yes, I've done that as well. I've decided to get a second modem and put it upstairs. I've noticed that Comcast just does not provide good WiFi, as now my laptop is getting terrible connection up there. You just can't beat an Ethernet connection, and I already have a cable and splitter up there. I want to thank you for all the help, though. Much appreciated!

Bad modem could certainly explain the issue. If I were you - I'd call Comcast to get a replacement.