yea your HD is not locked. easy prob to fix, it just helped another person out few hours ago. follow these steps. first thing is to put that 40 gb hd from the xbox back into the pc and load the xboxhdm back into the cdrom, then restart your pc and follow these steps. it's an easy fix.
1. Restart pc and load bios (click F1 or F2 or DEL whatever you use to get in)
2. Go to the Advance BIOS, and make sure primary and slave are disabled. Physically click the option none if the bios has the option none or disable, bios has different versions.
3. Then go to boot sequence and make sure it says 1. cdrom 2. Disable 3.disable 4. disable.... only cdrom should show.
4. Restart pc and go back to bios. you should not see the Xbox hard drive you have hooked up!!! IF YOU DO SEE IT MAKE SURE YOU FOLLOW THE STEPS AGAIN AND CLICK SAVE!
5. After this is done restart the pc and let xbhdm do its thing, now go into the lock hd screen, click yes and type lockhd -a <--- just like that.
Clicks ok then TURN OFF THE PC NOT RESTART!!!!
remember when you put back your old harddrive to reset all the bios settings, click save and restart.