Bing desktop was released through the windows update system,
Which is where you can Uninstall the update from,
Go to Uninstall a program or Programs and features,
On the top left click on View installed updates,
Scroll the list, it might take a minute or two to completely load all of the updates.
Right click it and click on Uninstall, it should be listed as, Bing desktop search.
P.S.
Change how you receive windows Recommended updates so when you uninstall it, it will not reload.