Setting up Windows 7 in VirtualBox can indeed be challenging due to its older architecture, but with the right configurations, it can work smoothly. I've worked with similar setups mostly for application testing, and here’s what I’ve learned along the way.
Firstly, it's essential to verify that the Windows 7 ISO is not only intact but also correctly mounted. Use the "Storage" settings in VirtualBox to confirm the ISO is attached to the right controller. Switching between IDE and SATA can sometimes solve installation issues.
In the "System" settings, ensure you've enabled VT-x/AMD-V if your CPU supports it, as this can significantly boost installation performance. Also, allocate a bit more processing power by adjusting the CPU slider to two cores, as this often helps with smoother installations in my experience.
Keep an eye on the "Network" settings as well. Sometimes turning off network adapters during installation can help avoid any glitches or errors related to driver compatibility.
Driver issues often arise with Windows 7 due to its need for specific hardware support, which modern systems might emulate differently. You might try adding the VirtualBox Extension Pack, as it extends functionality, facilitating better integration with USB devices and providing a more stable environment for Windows 7.
Once you have Windows 7 installed, make sure to install the VirtualBox Guest Additions. This step enhances the functionality of your VM by improving graphics support and enabling clipboard sharing and drag-and-drop features between your host and guest VMs.
Lastly, if performance issues persist, consider tweaking the allocated RAM and disk space. Although 2GB of RAM is the minimum, giving it a little more breathing room can help, especially when running legacy software.
If you're open to suggestions, try running the setup in "Safe Mode" within VirtualBox; it can sometimes bypass problematic stages of the installation process. If this is something you're interested in exploring further, just let me know, and I'd be happy to help guide you through it!