Buy a new kew from the dealer, when you receive it send the old key to the guy in the link below, he will repair it for about $40-$50. Now you will have two working keys, that's what i did.

http://www.bmwgm5.com/

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2002 X5 4.6is
1999 C5 Corvette
1992 Mitsubishi 3000GT VR-4
1994 Kawasaki ZX-9R
2005 Mazda 6 Wagon (Wife's)
1991 Mitsubishi 3000GT VR-4