How to update a record with primary key using stored procedure.

Can any one help me to update the primary key using stored procedure as I'm having an error
but when I tried to update the record using a condition it work, (LaptopID is the primary key).
But when I try to update the primary key with the second code it doesn't work as the condition (Where LaptopID=@LaptopID) will be changed, and I don't want to make another stored procedure with another condition when I update the record with the primary key.
the code I used to update the stored procedure is:
ALTER PROCEDURE Update_Data_SP
  (
  @LaptopID varchar(50),@StudentID varchar(50),@Manufacturer varchar(50),@Model varchar(50),@AcquistionYear varchar(50),@History nvarchar(MAX),
  @Comments nvarchar(MAX)
  )
AS
  Update Laptops_Table set LaptopID=@LaptopID, StudentID=@StudentID, Manufacturer=@Manufacturer,
  Model=@Model, AcquistionYear=@AcquistionYear, History=@History, Comments=@Comments

When I used a condition worked:

ALTER PROCEDURE Update_Data_SP
  (
  @LaptopID varchar(50),@StudentID varchar(50),@Manufacturer varchar(50),@Model varchar(50),@AcquistionYear varchar(50),@History nvarchar(MAX),
  @Comments nvarchar(MAX)
  )
AS
  Update Laptops_Table set LaptopID=@LaptopID, StudentID=@StudentID, Manufacturer=@Manufacturer,
  Model=@Model, AcquistionYear=@AcquistionYear, History=@History, Comments=@Comments WHERE LaptopID=@LaptopID

The thing is I want to update even the primary key which will not work because if I changed the the primary key the condition (Where LaptopID=@LaptopID) will not be valid.

Any suggestion or idea if there is any way I can update the record including the primary key in one stored procedure???