One partition is disappeared from my laptop, help

I have Lenovo Z5070 with hard disk 1THDD+8GSSD
i was trying to join my HomeGroup nd i just change the work group name nothing more then i found that my partition D (750Gb) disappeared!
i opened Disk Manager and i found that partition without a letter , i tryed to " Change Drive Letter and Paths " it shows an error "the operation failed to continue because the diskmanager isn't up to date, or restart the computer or the diskmanage" , i tryed to refresh nd reboot but nothing
then i made a mistake by make this partition as active so that blocked me for a while from entering nd it gives me BOOTMNG IS MISSING , for hours i try to fix it nd finally i did nd logged in again
but that partition is still not show up , i try many programmes for it , as EaseUS Partition Master 10.5 ,MiniTool Partition Wizard Free , it show the partition without letter too nd the data on it (i cant delet it its important data) but when i try to change the letter it failed !!
i try with CMD DISK PART ,it shows up in Volume but not show up in Partition and it is NTFS in the other programmes
here is some print screens , plz help

hey guys , i solved this problem and i will post how to help anyone else could have it

the mean reason for that is that i was joining my homegroup network so it makes a conflict with "partition table" of another laptop on the network , so i used this tool " TestDisk " and here is the steps to do it Have you "lost" a hard drive, partition or files in your computer? - Tech Support Forum

:)

You also need to have a letter assigned to any partition to have it read in Windows.

yes sure but i wasnt able to make a letter assigned for the MISSING partition with any tool that was the mean problem

This problem arises mainly because sometimes Windows refuses to release the drive letters of once present but now not present drives.

Once in a while or whenever a problem of this sort arises do a drive cleanup as follows:

Download v 0.8.1 of the drivecleanup.zip from Drive Tools for Windows.

Unzip it to a folder, say drivecleanup.

You will have two folders Win32 and x64 each containing DriveCleanup.exe for 32 bit and 64 bit respectively.

Remove all USB storage devices from your system including network drives ( disconnect from internet) , USB printers with Card Readers, USB hubs etc.,(except your Keyboard and mouse) and reboot.

Right click on the DriveCleanup.exe and run as administrator. (Use the *.exe file appropriate for your bit version of Windows.).

After the clean up act, reboot.

( When you plug in your USB devices after this cleanup these will be installed afresh. What you have done is to remove all non-present devices and drive letters/registry entries associated with them and start with a clean slate.)