JLinkARM.dll not found. please reinstall latest JLinkARM.dll

I use nrf51422 dk, device: s310 2.0.1 Then i want to download "bootloader" from example floder by keil 4 but it can't work and show up "JLinkARM.dll not found. please reinstall latest JLinkARM.dll "

i should i solve it?