First, my unlock would not have been successful without M3. Thanks for the excellent information.
Details: I currently have AT&T Wireless (blue SIM). Even though AT&T merged with Cingular, I had read that there was a chance my SIM would not work in a Cingular-branded L7. I decided to find out.
I put my SIM in and powered-on the phone. I immediately got "Enter Subsidy Password" - a sure sign that an unlocking was necessary.
Software: RSD Lite 2.7 and P2K Easy Tools v3..9. Before proceeding, I made note of my bootloader and firmware versions. I also confirmed that my phone was sucessfully detected by RSD Lite and P2k Easy tools. RSD Lite is (just) used to indicate that the phone is detectable - P2K does the actual unlocking.
Equipment: I bought a toolkit through Amazon that had all the proper-sized torx bits. I also had a spare alligator-clip and needle probe. Soldering those two together, I made my own grounding-device for the testpoint.
Process: I had watched the youtube video a few times to get my bearings. I also advise using a lump of clay or putty to hold the motherboard in place while you're grinding away a the metal shielding. It was thicker than I expected. About twice the thickness of a metal door on a 3.5" floppy disk. I went slow. After exposing the testpoint, I followed another recommendation in putting the motherboard back into the phone housing and screwing it down. This keeps it and the battery connected during the testpointing. You don't need to reconnect any of the cables at this point. After confirming that the battery won't dislodge from the motherboard, take the battery out.
Time to testpoint: Get the software ready first. I had RSD Lite open and waiting. In P2K Easy Tools, I selected L7 SLVR then switched to the Locks tab and checked the box labeled "Unlock SP" I then put my cursor on the "Do Selected Jobs" button.
Like the video instructs, plug in the USB cable to the motherboard. Then connect the ground to the metal-shield and put the needle-probe on the testpoint (REALLY tiny - have good lighting nearby). Insert the battery. When I saw RSD Lite detect my phone, I clicked on the "Do Selected Jobs".
Connecting to phone ...
Connected to: 'Motorola Flash'
Bootloader version: 0300
Sending loader to phone ...
Loader sent OK.
Read Flash ID ...
Flash ID: 89001088
It only took a couple seconds for my phone. But that was it. P2K instructed me to remove the testpoint (which I did) and I then disconnected the phone and battery for re-assembly.
No more "Enter Subsidy Password". This time, with my AT&T SIM, my phone let me inside.
Boot Loader: 0A.20
SW Version: R4517_G_08.C4.1ER
My motherboard had "BD 3" silkscreened at the top near the camera. I believe others may have BD 5...
sweet! I was too scared to do that myself. Something about taking a dremel to something that I don't currently have the money to replace...
i'm going to be leaving the US for a few weeks soon, so all I did was call Cingular/AT&T/who knows what they are, and asked for the subsidy code. They gave it to me without a hitch, especially since it was a business-related trip. Either way, it's nice, for sure.