When you say that the machine fails to boot, what tells you that it is failing? This probably sounds like a stupid question, but really, it's not. Are you assuming that it won't boot because it goes through POST and starts loading Windows but never gets to the GUI? How long are you waiting before assuming that it is hung and rebooting? Are you having problems even getting to POST, or do you see the Starting Windows... screen?
If you can boot into safe mode, go to device manager (system from Control panel, OR right click on My Computer, select properties, then Device manager tab, or just Windows key (flag) & pause key) and look in every category (skip system devices unless you want issues) and remove any devices that aren't currently installed. Many times, you will see multiple items under Displays, video adapters, etc if you have upgraded your hardware since installing the OS. (On business PCs, I have seen so many multiple monitor entries, and every entry is taking up space in your registry making it much larger and fragmented than it needs to be)
Make sure you look under ther network adapters and see if the dvice is still listed in there somehow. It may still be there in some form.
After removing the miscellaneous devices (if unsure, leave it), go to the network tab in Control panel and make sure the card is no longer listed there. If it is, remove it. Reboot into normal mode and see if your problem still exists.