How can I restore back OEM info on windows properties

The official way would be to wipe your hard drive and restore the factory image that set all of that info.  That may be possible via an OEM Recovery partition if your system still has it after your clean install, otherwise Dell for at least some systems allows a factory recovery image to be downloaded and used to create a bootable USB flash drive.  If you don't want to go to all of that trouble, then you'd have to either add that information back yourself or leave it as-is.  Since I don't really see any point in having that information given that I've performed clean, generic Microsoft installs on all of my systems for over a decade and have never wished that information was available for me to look at, I personally would do the latter.

You would need someone with an Alienware on factory settings to provide the OEM folder found in C:\Windows\System32

Once this is done you would need the following registry entry... This is taken from a Dell System so may be slightly different.

Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\OEMInformation]
"Logo"="%SystemRoot%\\system32\\oem\\SystemLogo.bmp"
"Manufacturer"="Dell"
"SupportURL"="http://support.dell.com"

yeah but can anyone here share the OEM folder (the original one). I know how to edit the registry but I mean is there any official way of doing this! Thanks a lot guys for helping me... I really appreciate this.

windows+R > regedit > enter