is it possible to install ubuntu on a existing drive which have some data in it?

Here some general note on install Ubuntu and howto to get a good ubuntu iso cd image (.iso) to burn on a cd:

- Here the steps to install Ubuntu 10.04.1 https://help.ubuntu.com/community/GraphicalInstall

- Here install Ubuntu video http://www.youtube.com/watch?v=XaqaDZZ_P0g&feature=fvw

Below there are some intructions to:
--- 1) Ubuntu prerequisites... and Ubuntu for pc with low power
--- 2) download the iso...
--- 3) check the md5sum of the iso image, please don't forget to check...
--- 4) burn the iso image to a cd ...
--- 5) install Ubuntu using the self made cd ...
--- 6) trouble screen at installation or at first boot after installation ...
--- 7) Ubuntu manual and online help...
--- 8) Relax and fun...

The main ubuntu site is this: www.ubuntu.com and the download location is this
http://www.ubuntu.com/desktop/get-ubuntu/download

--- 1) Ubuntu prerequisites: https://help.ubuntu.com/community/Installation/SystemRequirements

Ubuntu 10.04.1 release notes: https://wiki.ubuntu.com/LucidLynx/ReleaseNotes

https://wiki.ubuntu.com/LucidLynx/ReleaseNotes/ChangeSummary/10.04.1

If your ram is less than the recommended amount, you won't be able to install with the graphical installer,
but you might be able to use the Alternative cd, where you can use a text based installer - that uses less memory.
If your machine does have plenty of ram, you might want to try running Memcheck (which is also an option from the live cd, see below)
to just make sure your ram isn't failing.

- if your pc doesn't meet the Ubuntu prerequisites, you can try:

xubuntu http://www.xubuntu.org/get
lubuntu http://lubuntu.net/blog/lubuntu-1004-now-available-download
here a list from distrowatch: http://distrowatch.com/search.php?category=Old%20computers

- if you pc is a very low resource pc you can try different Linux distribution
  something like DSL http://www.damnsmalllinux.org/ or Puppy Linux www.puppylinux.org/ on your machine.

1.a) Please always prefer to download them using torrent if you can...

1.b) BE ABSOLUTELY SURE to verify the md5sum https://help.ubuntu.com/community/HowToMD5SUM
of the downloaded iso image BEFORE to burn it

1.c) burn it using infrarecorder if you are using Windows at lower speed you can do

1.d) boot your pc from cd and install...

--- 2) please download the 700 mb file http://www.ubuntu.com/desktop/get-ubuntu/download simply press on download button
To avoid download errors download the desired ubuntu iso install cd image using the torrent protocol.

- if you are using Windows please install a torrent client i suggest you http://deluge-torrent.org/
and download the iso using a .torrent link from here:
http://releases.ubuntu.com/10.04.1/ubuntu-10.04.1-desktop-i386.iso.torrent

--- 3) PLEASE BE SURE TO CHECK the md5sum of downloaded file to be sure it have no error https://help.ubuntu.com/community/HowToMD5SUM
Only if the md5sum number match with this: http://releases.ubuntu.com/10.04.1/MD5SUMS go to the next steps.

--- 4) burn the iso image onto a cd, to do it install and use http://infrarecorder.org/?page_id=5 burn the cd at lower speed you can do and activate the data verify

--- 5) insert the self made install cd into your pc cdrom drive and reboot your pc. YOU MUST NOT SEE Windows starting and you can try Ubuntu from cdrom and then install it

--- 6) If you have trouble with installation (the system freeze or you can't complete it) be sure to read the above suggestions, then:

Please boot entirely (you must not see windows starting) from Ubuntu live install cd and when the system start to boot from cd you will see two bottom screen icons (keyboard and man inside circle ) please press space (choose your desired language) then a screen textual center menu will appear to you with this items in it:

Try Ubuntu without installing
Install Ubuntu
Check disc for defects
Test memory
Boot from first hard disk

Please select "Test Memory" to deeply test your ram healty, if your pc freeze at installation or installation doesn't start.

Please select "Check disc for defects" and press enter to test if your cd-driver can read in a good way the live install cd... or if the install cd have some defective file in it.
Then please also perform a Test memory to be sure your pc RAM memory have not any issue

If you get a blank screen at boot after install or booting from the Ubuntu install cd please read:

http://www.ubuntugeek.com/how-to-fix-ubuntu-10-04-lts-lucid-blank-screen-at-startup.html

If you have trouble with intel8xxx graphic cards:

please try this: https://wiki.ubuntu.com/X/Bugs/Lucidi8xxFreezes

--- 7) Ubuntu Manual, it's very informative: http://ubuntu-manual.org/
Click on the "download Button" to download the latest PDF version.

The online help https://help.ubuntu.com/10.04/index.html

--- 8) Relax and fun
http://planet.ubuntu.com/ and Full Circle Magazine http://fullcirclemagazine.org/

To answer your question, the only way to install to the D: 'drive' without erasing data is by using Wubi. This installs ubuntu to a virtual disk within the existing ntfs file system and it can be installed and uninstalled from within Windows.
Otherwise, you'll have to split the partition represented by D: and install to the new partition (because you need a completely different file system to install Ubuntu - therefore it cannot share your existing partition.)

Yes, it is possible. I'm assuming from what you said, you have

1) C: is 40 gigs, with Windoze 7
2) D: is 106 gigs
3) E: is 2 gigs (most likely a usb flash drive)

Firstly, you'll want to defrag the D: drive. You can do this under Windoze. Or go to piriform and download the software degraggler. I suggest you download defraggler and use that instead of Windoze's defrag program.

Secondly, follow the steps that Marcobra had copied and pasted in the first response. It's a lot of information and you'll easily get overwhelmed, so follow it slowly, step by step. Or, take life by the horns and

1) download ubuntu
2) check that the copy you have downloaded has the correct md5sum
3) repartition your D: drive (you'll need a minimum of 20 gigs for ubuntu)
4) install ubuntu by choosing the option to install in the **largest continuous free space** on your D: drive (this will allow you to dual boot windoze and ubuntu)

Marcobra's posting has all the links you need.

OR

You might want to test drive ubuntu to see if it really works for you. The download page will show you how to do this. I suggest you use PenDriveLinux instead of the one at sourceforge that many people advocate. The PenDriveLinux' installation program is more current and easier to use.