Downgrade windows 7 Ultimate to Professional,Home Primium or any version

3.Now go for - HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\currentVersion.

  

 on the right side here is some information about your installed windows.

Now the important step you have to backup your registry by right click on CurrentVersion and then export it to some other partition of your Machine(pc).

Now delete all the key by double click on every string (example -BuildGui, EditionID, ProductName) each and every..
Thats it. Now it will look like as shown below:

Now exit registry. and restart your pc.
Note:- donot boot with your Windows 7 Disk
After login to your computer insert DISK and then hit the Setup.exe
then chose the second option donot update online (your os should have sp1)
then chose what else Os you want

it will check for compatibility

Start Upgrading (even this sounds absurd):

then this msg will appear , click next

now you done. leave all this to OS now take a rest or you can go for a walk also...

Now its time to cheer with welcome screen with Windows7 Home premium or what else version you install

 go to my computer properties and check all the things.

Thanks for visiting....