In the task bar a balloon with "MTP device has been found" is coming. How to stop this?

Start --> Right Click
Select Properties --> Select Properties
Select Taskbar --> Click Customise box
Click "Show hardware devices" (Some times you may see 'No title'. Select that)
Select "hide when inactive" (on the right)
Change it to "always hide"

This will allow you to use 'Add New Hardware' in Control Panel.

"always hide." This will allow you to use add new hardware, you can then delete the devices

To know what is a MTP device? click here.

Click here to know what is MTP?

My taskbar says a "MTP device has been found". What is this?

Devices like Mobile Phones & Portable Audio/video Players (with USB connectivity) are called MTP devices.

Did you connect 'Mobile Phone' or any 'Portable Audio/Video Player" in your USB Port?
If yes, you will get this balloon in Windows Task Bar.

Upgrade Windows Media Player to ver 10 or higher to stop this 'task bar balloon' and install MTP (Media Transfer Protocol). Click here to know what is MTP

What is MTP?

MTP is the short form of Media Transfer Protocol.
This protocol is required to download audio files  from digital audio players and movie files from portable media players like mobile phones.

By Installing Windows Media Player 10 or above you can enable MTP in your PC.