Citrix has fully archived all XenServer 7.6 binaries. You can no longer find the ISO on the main Citrix download portal (now called "Citrix Hypervisor"). Official support ended on June 24, 2022.
The installation ISO is a single DVD. The “Supplemental Pack” (DVD2) contained drivers and XenCenter – now available separately from archive.org or the main ISO includes XenCenter for Windows. xenserver 7.6 iso download
However, Citrix maintains a legacy section for customers with active enterprise licenses. Citrix has fully archived all XenServer 7
Follow this safe procedure to get a clean ISO: xenserver 7.6 iso download
