Half-Life

I had to buy Half-Life again. I legally own the original but due to the fact that my CD key has turned up missing I am no longer able to install it. I understand why companies are using CD keys to help prevent piracy and block cheaters from online games, but it's a real pisser when you have to re-buy a game over something so trivial. I would also like to point out the extreme price differences in the Half-Life Platinum Edition. Most stores including Target, Walmart (shudder), Best Buy, GameStop and EB World want $39.99 for the package while NewEgg only wants $19.99 and GoGamer wants $22.90. I don't why the huge price difference but needless to say I bought my copy from NewEgg.