I delete my device for sd

[help me]

it delete the device for sd, what do I do for has it again?, my computer is
windows vista home

 

[t-4-2]

it delete the device for sd, what do I do for has it again?, my computer
is
windows vista home

First, what is "sd"??
Secondly, What is " it " ??
Thirdly, What did you mean " -- what do I do for has it again " ???
I don't believe anyone, except yourself, knows what you were saying.
Please use simple sentences, and explain one more time what is your problem.