Something is really wrong here, let's see:
If you have NUSB insatalled, you don't need any other drivers for using a USB 3.0 pendrive in a USB 2.0 port/controller. The drivers are for the controller and ports, not for the device itself.
The numbers for the A-DATA are good, but not particularly impressive (and confirm it's working in USB 2.0 compatibility mode).
read speed : 20-25 MB[color="#FF0000"]/s[/color] or above
write speed : 10-13 MB[color="#FF0000"]/s[/color] or above
Now, a really fast USB
2.0 pendrive, like an OCZ ATV Turbo 8GB (SLC, out of production for at least one year already) can beat that easily:
Sequential Read * : 32.6 MB/s
Sequential Write * : 26.5 MB/s
*Test Size : 100 MB
These numbers are from one test I ran in 2009, when no USB 3.0 pendrive even existed, and using NUSB as the USB 2.0 stack.
You'd need a USB 3.0 add-on controller and port, and with that you might reach 133 MB/s for both sequential read and write (if card is PCI) or more (if card is PCI-e). Of course that requires a real good USB 3.0 pendrive, like the
RunCore Pro IV (aka Moon Drive, SLC) or the
Patriot Supersonic Magnum. Either, if plugged to a USB 2.0 port/controller should reach 35-38 MB/s for both sequential read and write, BTW.