30 minutes of angst when PC hung at boot due to external sata drive?

[sdowney717]

I recall couple years earlier gave my daughter an external Sata case with a 3.5 inch sata drive. I had tested the drive and had installed windows 7 on it in a different PC. I told her she can delete anything and start over with it.
So she brings it over, and it is working as expected. So this AM, I swap a PCI network card, reboot PC, and it hangs at the boot splash screen??!!

So start pulling cards, reset the bios, frankly was thinking the mb had just gone bad. So I start pulling connectors, keyboard, no, but the external drive was on and plugged into the USB and that was hanging the PC. I need to tell her to turn off the external drive.

So was their some boot conflict or why was it doing this?

 

[GokAy]

Maybe it was trying to boot from it? And couldn't due to drivers etc being different.