There are currently three reasons that people think they are being banned from Xbox Live with modded and upgraded Hard Drives:
1. The Marriage Theory: When you go on Xbox Live with an Xbox Microsoft marries your EEPROM to your HD serial in their database.
2. LPC scan: checks to see if you have a modchip installed.
3. HD contents check: checks to see if you have any illegal code on your C: and E: partions of your Xbox...
The only real way to not get banned is by using an original Xbox hard drive. This mod allows you to create an second hard drive that will fit inside the stock xbox case and allow you to use xbox live without the fear of being banned.
Necessary Equipment:
- 3.5" Desktop Hard drive (pre-softmodded)
- 2.5" Laptop Hard drive (8GB or bigger with unmodded but made a xbox hard drive using xboxhdm)
- 3 device IDE cable (buy it here or make it )
- 44 to 40 pin adapter for IDE laptop hard drive (Available at CompUSA)
- y-adapter for IDE power cable (radioshack)
- DPDT toggle (or slide, etc) switch (radioshack)
- Some extra wire
- Some velcro, mounting tape, electrical tape, whatever it takes
- Solder, soldering iron, and some decent soldering skills.
Wiring the Switch:
Begin by snipping the red and yellow wires about one inch from the connector that has dual wires coming out of it. Then clip one of the two wires as close to the base as possible, notice there is only one yellow wire and a nub, do the same to the red. Strip all ends about a 1/16 of an inch, just enough to make contact on the switch.
The one inch wires that go from the connector go to the long pins in the middle of the switch, note that there are 3 yellow on one half of the switch and the 3 red on the other half. Both yellow are red wires for IDE1 are on the left and both yellow and red for IDE 2 are on the right.
A few notes on two position DPDT (dual pole dual throw) ON/ON switch.
Dual pole means there are two separate circuits in this switch (1,2,3 is one 4,5,6 is the other)
Dual throw means that both circuits are flipped simultaneously.
Two position means there are two positions the switch can be in.
ON/ON means that when flipped in either position a circuit is on.
Lets talk about the yellow wires 4,5,6. When the switch is in one position 5 makes contact with 4, when in the other position 5 makes contact with 6. The same holds true on the other half of the switch so when in one position both 2 and 1 make contact and at the same time 4 and 4make contact (they do not cross over ie 4, 5, 6 does not contact 1, 2, or 3)
Connecting the Drives:
1) Set both of the drives jumpers to Master
2) Connect your 44 to 40 pin adapter to your laptop drive. Mount it using velcro under the DVD drive. It should be roughly where mine is pictured below. Beware of some capacitors and such on the motherboard ... that's why mine is placed where it is.
3) Hook up the 3 device IDE cable and cram it all back inside the xbox. The cable should go from the motherboard, to the DVD drive, to the laptop drive, to the desktop drive. Be sure the "short" end (the two 8" sections) goes towards the motherboard, and the "long" end (the 16" section) goes towards the desktop drive.
4) Connect your nice new hacked y-adapter to the laptop and the desktop hard drive. Here's what is should look like:
Best Site Ever 
Dual HDD's
Linear Mode
