If you haven't already done so, you will need to install the Windows USB System driver ( availble here Advent | Vega Internet tablet ).
Download and EXTRACT it a folder on your PC (eg. C:/ADVENT)
Connect your Vega to your PC, via a USB cable.
Connect your Vega to the mains, via the charger.
On the Vega, effect a FORCED POWERDOWN by long pressing (6 seconds) the POWERBUTTON.
Now to enter nvFLASH RECOVERY MODE...
Press and hold the BACKBUTTON for 2 seconds
Still holding the BACKBUTTON, press the POWERBUTTON for 2 seconds
But continue to hold the BACKBUTTON for a further 2 seconds.
Upon succesfull completion of this key press sequence, your PC will either direct you to install the USB System driver (in which case, point it to the folder as detailed above)...
...or it will 'ping' the 'found new hardware' sound
Now, on your PC, you can double click on the MODDEDSTOCK .exe (or whatever ROM you wish to nvFLASH).
PS. as an aside... I've never heard of moduleap.apk...