more theoretical than practical.

The simplest obvious attack vector is if the WiFi module is enabled in BIOS (assuming it's a setting) and your PC were accidentally configured to connect to any open WiFi network. The attack is that the hacker would setup an access point near your home and let your computer use it. There are two opportunities from there, 1) a gap in your firewall or the security of any service allowed through it, e.g. is your file sharing protected by a password? 2) any traffic you're sending to the internet (assuming somehow your traffic was routed through that and not your hard connection which would not be the default at least on windows) could be seen, but unless they've somehow manipulated the certificates on your computer, would be encrypted (as long as it's an httpS site) and therefore useless.

The second requires there to be some vulnerability on the motherboard. That'd require the hacker to know you had that motherboard, know about the vulnerability, have the capability of actually running the exploit which is usually non-trivial, and have equipment installed near you.

The weakest link in your security is most likely somewhere else.