Drive D 'Extend' ... can't

1. Your D drive is a factory Restore Partition provided by Dell to recover your
computer to a factory shipped condition and should not be used for anything
else.

If you made recovery DVDs, or order them from Dell, you can delete the partition
and extend C to take up the recovered space. Or you can shrink C (although you
might have limited success with this because of the page file) and create a
larger D volume. I believe D cannot be extended as it is now because it is not
NTSF formatted,

2.

Most branded computers ship with a so-called recovery partition. Best
advice, leave it alone! It is the only life saver you system probably
came with. Example you probably didn't get a Microsoft Vista DVD did
you? So if you ever have to repair your system if you mess with the
partition that is suppose to be able to recover your system and
restore it to it's original out of the box condition, you're  s crewed.

You are correct in that in order to expand the size of one partition
you need to get the space from another partition or from unallocated
space (non assigned disk space on a hard drive).

Since you have only one hard drive you gain nothing in the way of
better performance by carving it up into other partitions. With hard
drives as cheap as they are you would be better off adding an
additional hard drive or if you must fiddle, leave the D drive alone
and just create another drive from excess UNUSED space on C.

It is generally easier and SAFER to use third party partition
software. Just be sure whatever you pick is Vista certified. I simply
don't trust Microsoft to do a decent job with something that critical.
If you want to be a river boat gambler, reduce the size of "C", which
should create some unallocated space, then once that job is done and
you confirm that Vista now sees the allocated space make a new
partition from it leaving D alone.

So in your example you would end up with something like this:

C: 30 GB
D: 10 GB
E: 180 GB

NEVER short change your root directory. It will continue to eat up
space by default from normal system activity. The worst thing you can
do for performance it trying to make Vista run in a shoehorned space.
So you should allow at least 20 GB for the OS and swap file, then a
good margin for growth. I just used a rounded up figure for E, it
should be the size of whatever is left over.