What is the best way to debug driver install trouble?

Running it through the install on clean machines a few dozen times (On Win 7 64 bit) I've noted random blue screens when the bridge installs. When it doesn't blue screen it doesn't work. It just shows a yellow triangle in device manager.

Error Code: -5005 : 0x8000ffff
Error Information:
>Kernel\KernelMedia.cpp (95)
>SetupNew\setup.cpp (811)
PAPP:Silicon Laboratories CP210x VCP Drivers for Windows XP/2003 Server/Vista/7
PVENDOR:Silicon Laboratories, Inc. (http://www.silabs.com)
PGUID:2AEE35FC-0EF1-4DAC-BAF1-790BD087175D
$16.0.0.328
@Windows 7 / Server 2008 R2 Service Pack 0 (7600)
IE Version: 8.0.7600.16385

The blue screens may be related to the Keyspan USA-19H USB to Serial converter on the systems. The dump file refers to trouble with the keyspan during the install of the CP210x drivers. Uninstalling the keyspan driver has eliminated the blue screens (but they were random so it's hard to say - keyspan rev 3.7s).

Next, 6.1 doesn't install on Win 7 64 bit because of a driver signing problem: Quote Device Manager

"Windows cannot verify the digital signature for the drivers required for this device. A recent hardware or software change might have installed a file that is signed incorrectly or damaged, or that might be malicious software from an unknown source. (Code 52)"

I guess in Win 7 no driver sig means drivers won't load.

From a software standpoint the comport doesn't exist and won't open.

Next: the drivers don't really uninstall and you really have to jump through hoops to get the system cleaned off.

Win 7 (and Vista) keep a copy of the drivers in Windows\System32\DriverStore\FileRepository\ so if you uninstall the drivers it can reinstall them. So if you upgrade (or downgrade) your driver and you fail to delete the registry entry for all the CP210x's you are using you'll find it pulls the old driver out of the driver store and uses it.

You manage the driverstore with pnputil but it appears the driverstore easily gets loaded with zombie versions that can't be cleaned out (unless you install the "TakeOwnership" registry hack and Take Ownership, grant yourself rights, and manually delete the zombies).