Data partition disappeared

I have somewhat the same problem as this guy has: http://windows7forums.com/windows-7-installation-upgrade/14819-c-drive-no-more-visible.html
I read that you guys might need the Diskmgmt information in his topic so here it is:

I had the RC which was dualbooting fine alongside XP. Then I got the RTM, burned it, booted up with it, deleted and formatted the partition on which 7 was (which was the C drive) and installed the RTM.
When I did this I noticed that the os selector had disappeared. So I installed EasyBCD to try to fix the bootloader but I think I messed up in this stage.
Cause when I tried to boot in XP, I got the "Error loading operating system".
Tried some things to fix it, (which involved reinstalled 7 again just to boot up in it to try to fix the bootloader), didn't work, gave up.

Put in the XP cd, deleted the XP and 7 partition, and created a new 100GB partition and installed XP on it. ( My 400GB Data partition was still visible and accesible in this stage).
Then I put in the 7 dvd, booted it up, created new 100GB partition out of the leftover unformatted space, and installed it.
No problems during installation, computer rebooted, I got the nice bootloader screen with the "Earlier version of windows" and "Windows 7" option. Everything still ok, boot up Windows 7 and there I notice that my Third partition, with all my data had disappeared! =S
I'm thinking wth is this, I reboot into XP, and there it has vanished as well!

What should I do now?
I want to get atleast the Data back, I don't care if I have to format my entire drive again and install XP and 7 all over.

I just booted up with the XP cd and act like I would install XP to get to the partition manager part, there it also said the 400GB of Unallocated Space.

Soo I'm guessing I might have accidently deleted the partition when I was installing 7... =(

So now my big question is: Is it possible to still recover the data?

You need to leave that partition alone for a bit. Search this site/web for something called Recuva. SF has a couple of members that can help you with this.

But yes, it is possible to get your data back - but it may not be pretty.

I'm trying to recover it by using Active@ Partition Recovery.
Is this program any good? I sure hope so.
If it's not, can somebody know a better one that will very likely do the trick?

Finally..
I was able to recover the partition with all my data with Acronis Partition Recovery!
I took pretty god damn long, but it payed off.

Hi, just wanted to let you all know I lose my data partition regularly (but not every time I boot) on my Dell latitude. I've used partition wizard home edition 4.1 to resize my partitions (both OS and data) when I'd just installed windows 7. My standard method of recovery is to recover the partition with partition wizard and reattach the drive letter with disk management. Recently I removed and recreated my data partition, hoping that would fix my problem. However, this morning again no D: partition.

any ideas on how to fix this would be appreciated.

Post back a screenshot of your full Disk Management drive map, using the Snipping Tool in Start Menu and attaching file using paper clip in reply box.