Error while installing Win7 64bit; 'Unexpected error'

I just ordered the Win7 DVD from Amazon, so it actually wasn't that big of a deal for me to go back in and (attempt to) cancel the order. Since it's the weekend, it wouldn't arrive until Tuesday at the earliest anyway, so I doubt much has been done on their end to complicate things.

As I mentioned earlier, though, I'm already using that .iso, but for the sake of doing so, I'm downloading another copy that I'll use to re-do my bootable USB and try to clean install again.

Thus:
1. In progress.
2. Waiting on download to complete.
3. Wiping drive. Nothing I care to back up.
4. Don't have any recovery disks, so eh.
5. Got Belarc, will run after installation of Win7.
6. Key is on my CD case, next to me.
7. Necessary installers (read: adapter installer) already loaded on secondary USB device.
8. All other peripherals have long been disconnected, and I just ran diskpart clean, so there's nothing left to worry about anyway.
9 and on. Waiting on installation to complete further steps; I'll continue to update my progress as things go on.

Sounds good. Keep us posted.

First download of the .iso registered as "invalid .iso" by the Win7 USB/DVD tool; tried renaming, didn't change anything. Deleted, downloading new copy.

Whee.

Install the chipset drivers from your computer or mobo maker's Support Downloads webpage. See if that stabilizes Explorer enough to install Wireless/Ethernet driver and get online to Update.

From here: GIGABYTE - Motherboard - Socket 775 - GA-EP45-UD3P (rev. 1.0) I grabbed the Intel Inf drivers.
I can't run the .exe from my USB, and I can't install from the desktop either.

Try it in safe mode, or will there be no difference?

Try it to see.

Plain reboot seems to have reset the Explorer problems, but I installed the chipset drivers anyway, just in case.

Well, reset the explorer problems long enough for me to install my wireless, at least. Internet connection seems to be working, but Windows Update gives me error 8024001b, which google says is due to a pending update to windows update. Well and so, but my ability to restart the computer was having issues due to Explorer crashing again.

Task Manager -> Log Off; log off started going before Explorer crashed, but I didn't have enough time to copy down the error code before the log off finished.

When Explorer starts crashing, should I just try rebooting and hope it fixes itself?

Rebooting is good during setup.

Will it stabilize in Safe Mode with Networking?

Make sure you know the correct mobo version 1.1 or 1.6 then look in the small dropdown at BIOS updates to see if there is a newer one available than the one shown on BIOS splash screen or in Belarc Advisor.

Test your RAM and HD to clear hardware as well as other Troubleshooting Steps for Windows 7.