Consequences of Windows Genuine Advantage Warning?

On my desktop at home, the only reason I boot Windows is Team Fortress 2. Lately Windows Genuine Advantage has been telling me that my Windows is illegitimate. I get a black screen with a notification that says I need to validate my license blah blah blah.

I could locate my Windows key, try to validate it, call Microsoft, whatever, but really I can't bothered. What's the worst that can happen to me if I ignore the WGA message?

You will get only critical updates. If you don't mind possibly missing out on some updates that might make Windows work faster, or something along those lines, then you shouldn't have to activate it. But I agree that it's just proper etiquette to validate it, even if you only use it to play TF2. There's always the option that Microsoft will eventually send a "critical" update that could make your "pirate" copy cease to function, as they did previously.

People are implying that this guy is a pirate, but that isn't the case. The clue here is in his statement "I only boot Windows to..."

If I had to guess, he's using a Mac with Boot Camp. I have seen the Windows Genuine Advantage process get thoroughly confused if (for example) you boot into Windows, reboot into Mac OS, and then run Windows on your Boot Camp partition from within VMWare or Parallels.

Each time I do this (and I've done it on three different machines now...) I end up on the phone to a call center in India where I politely explain the situation and they give me the unlock code to fix it. But boy is it a pain in the neck.

Answering the actual question, at some point Windows will refuse to proceed until you enter the right code. Then you'll be on the phone to India. Good luck.