1. Unplug all drives and connect the 2TB drive.
2. Start the W7 install, and stop it after it starts writing to the disk.
3. Reconnect your 750GB drive and boot to XP (or boot to a Live CD/USB with partition tools on it)
4. Use a partition tool like Partition Wizard, or Gparted to delete all partitions W7 created except for the first little 100MB partition.
5. Expand the 100MB partition to occupy 40 or 50 GB (how much you think you will need for your OS and programs), and create another partition to consume the rest of the space.
The above procedure will allow you to install W7 on an aligned partition, but without the small System partition. This keeps everything needed for the install on just one partition. If you will be using Bitlocker- requires motherboard support- you need the small System partition, and you can continue the W7 install instead of aborting it in step 2.
6. Again disconnect the 750GB drive, and install W7 to the first partition that you have prepared for it in the above steps.
7. When W7 is finished installing, change the location of the user folders to the 750GB drive. (Log in as user > right click a user folder such as "Downloads" > select Properties > select Location tab > change the drive letter from C to the partition you want the data to reside > click OK a couple times)
8. Copy the data from your 750 GB drive to the appropriate user directories in the W7 libraries. If you have more than 400GB of data on the 750 drive, you will need to move the data to the 2TB drive before copying it to the W7 libraries (which would now also be on the 750 drive)
Every time you boot to the XP install, it will clear all your restore points from the W7 install. To fix this, you need to make the W7 partition not visible to the XP OS. If I remember right, this can be done by simply removing the drive letter from the W7 partition from the XP Disk Management window