.But we can not copy directly from GAC .Finally i have achevied this way .
Goto Start -->Command prompt
Type in Command Prompt --> subst Z: c:\Windows\Assembly
Click on enter
Note: subst is a command which creates a virtual drive
The abouve syntax creates one virtual drive "Z" and copy all dlls from GAC
-->Now you can go to Z: drive and copy your rerquired dll
