What USB generation is the new adaptor? What USB generation is your Laptop port?
We can try to tweek it tho!
Ok try this:
Go to www.speedguide.net
On the left hand side, you will see a link for a TCP OPTIMIZER. Click on it, Down load the client in the top middle of the next page, and run it as ADMIN.
After you run it, you will see a slider, set the slider to the speed that you got from your speedtest. Click on Apply changes. Reboot.
Let us know if this worked, and we will explain why it makes a difference in very simple terms!