Connect your Xoom to your PC, make sure USB debugging is enabled, open your command prompt, type the location of your tools folder, for me its,,
cd/sdk_tools
Then type
Adb.exe
Next
Adb devices
You should get a string of numbers and letters, then you know your Xoom is recognized.
Make sure you copied all the files from platform_tools to the tools folder or vice versa. All the files need to be in the folder your running commands from.