B1/B2 L2 query

[b1b2L2]

Hi I have a L2 visa issued in Jan 09, valid until Sept 2011, and a B1/B2 visa issued in May 2009, good for 10years. I went for B1/B2 stamping as my spouse who has L1 has not traveled to USA because of some project delays, and right now I am in United States on B1/B2 status. My spouse who has L1 will be reaching USA shortly; my question is whether I can change my status from B1/B2 to L2 without leaving USA? If that is not possible , and if I have to go back to India, and want to travel back to USA on L2 visa, do I have to go for L2 stamping again? I don’t see any cancellation stamp on my L2 visa. Is it still valid?

Please help……

Thanks in advance