When you boot from DVD your root path, /System/Library/... will be on the partition you booted from. In this case that is your DVD.

Extensions folder on your HDD will be:

/Volumes/~PartitionName/System/Library/Extensions/

list your Volumes to find the partition name where you installed SL.

(example)
/Volumes/Snow/System/Library/Extensions/

If you can't see your usb drive try with Disk Utility first. Plug it in then try to mount it in Disk Utility. If it won't go burn it on rewritable cd or dvd.

Again, pay attention when copying.

/Volumes/~CDPartitionName/fakesmc.kext to /Volumes/~HDDPartitionName/...

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