I sometimes have the same difficulty. Here are some things to try... make sure you're using the cable that came with the tablet. If you're using a usb hub, try plugging it directly into the laptop. Make sure Windows7 is set to automatically download drivers: in the Devices and Printers area, find the device that is the name of your laptop, right click it, find and click the item "Device Installation settings" and from there you can tell windows to automatically download drivers or not. I think one time I got so frustrated trying to get my laptop to recognize the tablet I plugged the tablet into my son's desktop and it worked just fine. Obviously that last doesn't help if you don't have a second computer available.
Somewhere, I think in the tf701-TWRP specific thread, is a link posted by sbdags where you can download a flashable .zip version of the recovery, meaning you can flash it from the existing recovery. That's how I flashed TWRP to my tf701 and it worked fine.
Hope something in there helps you. Good luck.
edit: in this thread
http://xdaforums.com/transformer-tf...overy-kang-twrp-tf700t-2-8-x-xarea51-t3121989 post #15 has the flashable .zip.