"Access is denied" when installing original drivers on Win7Sp1

[Guest cefn]

When following the Yaudig pdf instructions for installing the original vega boot-recovery drivers (which I downloaded yesterday from http://www.myadventvega.co.uk/ in an archive called SystemUSB.zip ) I hit a total dead end after Windows has identified and tried to install the drivers against the APX device.

It simply shows the following three lines after following the Device Manager "Update Driver" sequence...

"Windows found driver software for your device but encountered an error while attempting to install it

NVidia USB Boot-recover software for Mobile devices

Access is denied"

Having bottomed out all other options, I'm trying to use some kind of nvflash .exe to completely replace the image on my Vega (following an attempt to install a modaco Rom through clockworkmod, currently it simply shows Booting.... in yellow text whenever I turn it on, and I can no longer reach Clockworkmod, not having any button-push sequence on this device to reach it).

I also gather nvflash is the only way to go when trying to install more recent roms which need a different partitioning layout.

I've been trying to configure a machine with the right drivers to be able to run any of the various .exe files available to nvflash the device. I've picked up a Win7 machine from a friend and proven that the account I'm using has Local Administrator permissions.

This "access is denied" is a pretty unhelpful error message and worries me that I'm too late following these instructions (e.g. Windows7SP1 has changed something fundamental, and the drivers don't work any more?)

Is there anything else I can try to get functional nvflash drivers on Windows7SP1 to accept any ROM at all, (based on Moddedstock repartitioning or not) as I've followed every available route I can discover to get a working rom on this tablet, and have no obvious options left.