Better login speed when system and boot are on separate drives?

My PC dual-boots Windows 7 on each of two separate HDDs. Both drives have their own boot partitions, but only one drive has the system partition. Despite all my attempts to strip down services and fine-tune the performance of both, there is a noticeable lag between login and the appearance of the Win7 desktop when I boot to the Win7 disk that contains the system partition. When I boot to the Win7 disk that doesn't have the system partition, the desktop appears almost immediately after I enter my password.

Does the placement of the boot and system partitions contribute to this difference in login speed? When your boot and system partitions are on different drives, does that improve performance because--maybe--Windows is accessing both the system and boot partitions simultaneously?

This isn't a huge problem--both systems run great--but I'm planning on decommissioning the Win7 system with the slower login time so that I have only the faster one remaining, but if having the system and boot partitions on the same drive causes this lag, I want to know this in advance.

I have already read about the Win7 hotfixes regarding the long login times with solid-colored desktops and it doesn't apply to my system.

Thanks in advance.

Never mind. I solved my problem as follows:

(Note: My system was configured so that the Primary Master (PM) drive, which contained the Win7 installation I wanted to get rid of, was first in the boot order. The Win7 installation I wanted to keep was on the Primary Slave (PS) drive.)

1. Restarted computer.
2. Entered BIOS menu and re-arranged the hard disk boot priority so that the PS drive was first.
3. On restart, there is no menu to select the operating system; it boots directly into the Win7 installation I wanted to keep.
4. Analysis of the disks in Disk Management found that my desired Win7 installation was now marked as the System (exactly the result I was looking for).
5. From Disk Management, formatted the PM drive (which is now not marked as System or Boot) containing the Win7 installation I wanted to get rid of.
6. Rebooted and still no problems--boots directly into the Win7 disk I wanted to keep and the other drive is now an empty D: drive.