Expand disk space on D:

That is exactly what programs such as the highly regarded Partition Wizard CAN do, that are very complex functions that do not seem to be supported by standard built-in Microsoft services. Or, it just seems very straightforward and logical and intuitive with PW, which gives one a feeling of comfort as you "tamper" with your physical hard drives.

PW can certainly shrink the current primary partition (C), then resize the "extended partition" partition (to its right in the picture, containing the logical D partition inside of it, to the left of the 14GB un-lettered OEM partition which is no doubt a "primary" partition as well) extending it to the left to pick up the free space made available by the shrinking of the primary C partition to its left. It will all end up exactly as you want... whatever the sizes and drive letters you want to end up with.

That "logical" D partition is at this moment the one and only logical partition inside of the "extended partition" (its own primary partition, between the C-primary and OEM-primary). But in theory, any number of logical partitions COULD further be defined within that single primary "extended partition".

So, in that picture, there are a total of FOUR primary partitions on the drive (which is the physical maximum number of primary partitions allowed on a basic drive structure), described by the "boundary box" (in one of the early sectors on the physical drive). The 200MB "system reserved" (also un-lettered) primary partition is the first, and is used by Win7 for the boot manager files. C-primary is second, "extended partition" primary is third, and OEM-primary is fourth. That's it.

PW will have no problem shrinking that second (C) primary partition, extending the third primary "extended partition" to use all of the newly available space from shrinking C, and then allowing you to either re-size D-logical inside of the "extended partition" or move/resize, create new additional logical partitions inside that "extended partition", etc.

Just for comparision, PW's presentation of my own 4-drive situation is as follows. Note that with the exception of the "boot drive", you do NOT need to use ANY primary partitions on a drive. In this case the ENTIRE drive is allocated to the one single "extended partition" (which of course is actually a primary partition) inside of which any number of logical partitions can be defined, and lettered any way you want. This is all done by PW.



Just in passing, the reason my situation does not also reflect a 100MB "system reserved" partition is because I already had WinXP running, to which I added Win7 as a second bootable OS. The already existing "boot partition" (where WinXP still lives) thus contained the WinXP version of the boot manager files. The Win7 installation (onto a second partition, which really can be to a primary or logical partition... either on the same physical drive or even to another physical drive) then modified the existing boot manager files on the "bootable" WinXP partition and set up its own INI files to define the bootable OS locations. So the boot manager seen when I now boot is not the original WinXP boot manager, but rather the Win7 boot manager (actually, it's not even that... as I use EasyBCD, which is a very user-friendly free 3rd-party replacement product for the official Win7 boot manager).

Thus no new "system reserved" (bootable) partition was required, as it would be for a brand new 1-OS single Win7 situation. The existing WinXP bootable partition was perfectly acceptable for purposes of launching Win7's boot manager.

Download Partition Wizard as suggested by dsperber.
It is used by many members on this and other forums, this software is free and very reliable.
I use it all the time.

Make an image backup of your data on the C and D drives, just in case.

Open Partition Wizard.
Select, click on, the C partition.
Select 'Move/Resize Partition' in the left side box.

In the window that opens, use the slider in the Partition Wizard (PW) window, first the C partition, take the right side and slide it to the left making the partition smaller by the amount that you want to add to the D partition.
Click 'OK'.

Select, click on, the D partition.
Select 'Move/Resize Partition' in the left side box.
In the window that opens, you will see 'Unallocated Space Before' click the down arrow until it says 0 or select the number and enter '0'.
In the partition box, just below 'Size And Location', select and hold the right slider and move it all the way to the right.
Now both the 'Unallocated Space Before' and 'Unallocated Space After' boxes should have '0.00' in them.
Click 'OK'.

In the upper left corner there is a large blue check mark, under it it says 'Apply', click it and follow all instructions, the computer will shutdown and perform these actions before it re-starts.
This may take some time, just let it finish.

It's really easy, after the first time.