To install Windows Vista on a GPT partition without wiping your Windows 10 partition, you can try the following steps:
1. Before proceeding, please make sure to back up all important data on your secondary partition as the process involves making changes to the partition table.
2. Download and install a third-party partitioning tool like AOMEI Partition Assistant, MiniTool Partition Wizard, or GParted. These tools provide options to convert GPT to MBR without data loss.
3. Launch the partitioning tool and locate the secondary partition where you want to install Windows Vista.
4. Select the secondary partition and look for an option to convert it from GPT to MBR. The specific steps may vary depending on the tool you are using, but it should be mentioned in the documentation or help files.
5. Once the conversion is complete, you can try installing Windows Vista again using the 64-bit SP2 disc. Remember to boot from the disc and select the newly converted MBR partition as the installation target.
If the above steps do not work, you can try the 32-bit version of Windows Vista instead. However, it's worth noting that installing an older operating system like Vista on a GPT partition might cause compatibility issues with newer hardware and software.
Additionally, it's important to mention that Windows Vista is an outdated operating system that is no longer supported by Microsoft. This means that you may encounter compatibility issues with newer hardware and software, receive limited security updates, and face potential compatibility issues with drivers and applications.
If your intention is solely for testing purposes, you might consider using virtualization software like VirtualBox or VMware to set up a virtual machine with Windows Vista. This would allow you to run Windows Vista within your existing Windows 10 installation without the need for partitioning or making changes to your system.