Thanks to your advice, I was able to successfully install Windows 7 without that annoying System Reserved partition. However, there is just one peculiarity that remains: Disk Manager reports my D drive as "System" even though my C drive is the one that contains the Windows 7 installation. Both drives are marked as "Active" and "Primary Partition," and my C drive is marked as "Boot," as it should.
How can it be that my C drive is marked as "Boot," yet my D drive is marked as "System"? How can I change my C drive to be marked as both "Boot" and "System"?
Finally, I should mention that Disk Manager also reports Disk0 as the D drive, and Disk1 as the C drive (on which Windows 7 is installed). I strongly suspect that the installation detected my drives in the wrong order, since the one I use less would obviously be a bit faster. Could this be the reason why D is marked as "System"?