I recently had a drive fail and had to format and reinstall win 7 x64. I thought i installed it on a different drive, a 320GB drive. Although when i go into Administrative Tools-etc- Disk management, my "system reserved" allocation is on my 750GB, but my "C:" drive, which does not have a "system reserved" is the 320GB HDD.
I'm a little confused here... do you have two copies of Win7 installed and available, through a Boot Manager menu that is presented to you at boot time?
Or do you only have one copy of Win7 installed, on the 320GB drive, but you also have the "system reserved" partition still on the 750GB drive, along with the originally installed and now obsolete and not-used Win7 in a large partition on that 750GB drive which used to be C?
I'm sure that at the moment, your 750GB drive is shown as "hard disk #1" in your BIOS setup, which is why the "system reserved" partition got built there when Win7 was first installed onto that 750GB drive. The "system reserved" partition contains the boot manager files for Win7 (even in a 1-OS environment), and is marked as the "active" partition on the drive. That's how the booting process proceeds... BIOS -> ACTIVE partition on hard disk #1, i.e. "system reserved" where boot manager files live -> C partition on that drive, in a 1-OS world.
If you had changed your BIOS settings to show the 320GB drive as "hard disk #1" before you reinstalled Win7 to it, then the Win7 reinstall would have created a new "system reserved" partition" on that 320GB drive, marked it "active", and installed Win7 into a second large C partition on that drive. The 750GB drive would have been totally ignored.
Sounds like you didn't change the BIOS to point to the 320GB drive as "hard disk #1", and that's why you ended up the way you currently see things. You've got the 750GB drive as "hard disk #1", and the "system reserved" partition on it as "active". The new Win7 install is now on a single large partition over on the 320GB drive (and the old Win7 partition on the 750GB drive is just obsolete). So the BIOS boots to "system reserved" which is "active" on the 750GB drive (hard disk #1), and then checking the boot manager files really boots from over on the C-partition on the 320GB drive where your one reinstalled Win7 now lives. The old Win7 on the 750GB drive C-partition is simply not pointed to by the boot manager menu any longer (I'm guessing), because you still have a 1-OS world (although odd, because "system reserved" is on 750GB and Win7 is on 320GB).
It may actually be possible to just COPY that "system reserved" partition from 750GB over to some unallocated space on the 320GB drive using Partition Wizard, and then mark it as "active", and change the BIOS to point to 320GB drive as "hard disk #1", and have it all work. You may need to use Partition Wizard to shrink the Win7 partition on the 320GB drive (either just a little, or maybe a lot and create a D partition on the drive as well, along with leaving unallocated space for the "system reserved" partition you're going to copy over from the 750GB drive).
All of this should be done with the STANDALONE BOOT CD version of Partition Wizard I mentioned above, as you're fooling around with all of the basic system partitions. But the more I talk about it, the more reasonable and do-able it sounds.