You should know that chkdsk doesn't actually check the HDD, it checks the filesystem. It checks the contents of the drive, not the drive itself to put it another way. So just because chkdsk says things are fine doesn't mean things are actually fine.
Second, make sure you remove ALL USB devices from the laptop and try booting then. I know someone who has a Dell desktop that would do the exact same thing (only it was more like 2-3 minutes) when a specific external HDD was connected. An older Dell desktop booted just fine with the same drive, same cable, etc, so sometimes systems are just picky that way.
Third, unless you know what you're looking for, you probably shouldn't be messing around in the event viewer. You'll see hundreds or even thousands of warnings and errors, all of which are completely harmless and can be ignored. It takes a long time to build up the experience to separate the signal from the noise in that place, and even then it usually takes to long to find what you're actually looking for, so even a lot of experts don't bother. Case in point is the errors you're mentioning are almost certainly a result of your power profile restricting the CPU to conserve power. When the proper conditions are met, the CPU will be unshackled, so to speak. The other one just means the program didn't respond within the expected time allotment, but that could just be because the system is taking longer to boot than it should, it doesn't mean much of anything at this point.
Also, unless you have some other GPU/IGP on that system, getting rid of the video drivers is only going to make matters worse.
Now onto a follow-up question: Does the system appear to perform normally once it boots? If it seems significantly more sluggish, I'd be starting to suspect very strongly that you have a bad HDD. Also, while you were waiting for all the updates to download, did you have the Windows firewall running? Did you happen to do any web browsing to help pass the time or try and install some of your usual assortment of programs while you waited? If so, malware is a very real possibility. The sad fact is it usually doesn't take too long before "gold" releases of an OS reach a point where they can be exploited within minutes of being connected to the Internet. You don't even have to do anything. This is why in ages past people would slipstream service packs into the installer, but that stopped being a possibility with Windows 8 and the bizarre move to make everyone download the 8.1 update on every single system, every single time.
If it were me, I'd figure out what brand HDD was in that unit, go to that company's website and look for a diagnostic program I could run. My guess is either you've got a dodgy USB device or a failing HDD. If it's the latter, you'll get a lot better service out of ASUS if you use a fake name with an obvious Asian sounding last name. If you happen to already have one, bonus for you, but otherwise create a throw away yahoo mail or gmail account with a last name of "Chen" or "Phan" or something like that. That can make the difference between someone making you go through every single troubleshooting step there is before giving you an RMA to just handing you an RMA and maybe even a shipping label after explaining what you've already tried. Sad, isn't it? This long after the whole civil rights movement, we still have plenty of companies, particularly in Silicon Valley, who just completely thumb their nose at these laws.