The upgrade from 7.51 to 7.53 can be done using this ISO image. You just need to run the setup.exe binary.
Please note that NNM 7.xx is out of support and reached EOL for some time now. We can no longer provide download links for the 7.xx products because of legal reasons. We did not renew contracts with 3rd party SW vendors (such as Solid DB etc).
HP Support If you find that this or any post resolves your issue, please be sure to mark it as an accepted solution.