Ziemens

Assuming that Mr. Stefan is correct, there is software that can keep the ISO mounted through a restart (persistent). 

WinCDEmu [link] is mentioned [here] and [here].

 Kindly, where can we find the iso image of the dvd , to be installed by the WinCdEmu ? 

It is not clear what you may be thinking of.
The ISO files on the following web page perhaps? 
[LINK: SIMATIC STEP 7 incl. Safety, S7-PLCSIM and WinCC V17 TRIAL Download]

But that is not a free lunch. It is only a trial version that still needs a license for full time use.

Ziemens

Kindly, some older Siemens Tia softwares are requesting a real Dvd to be able to install properly. But, we do not have any Dvd on our new laptop. So, we were considering making some virtual Dvd, to put the old softwares in it, and install them as required. 

The older software all has some downloadable format. The trouble is that Siemens has recently removed many of the old version from this support site. You can contact Siemens and ask them for the installable files. 

Otherwise you will have to invest some web research on how to make an ISO from a DVD. Or simply make a copy of the DVD on a removable storage media.