If you manage to find a clean copy on an old USB stick, treat it with respect. Run it on a VM, smile at the Aero folders, and remember 2013—when a portable icon pack was the ultimate act of desktop defiance.
Enter the niche but enduring solution: —a software relic that promised to drag your modern (at the time) Windows 8.1 interface back to the glossy, transparent, and familiar look of 2009. windows 7 icon pack by 2013 windows 81 portable
Use Task Manager’s "File > Run New Task" to navigate to your portable folder. Run Apply_Win7_Icons.bat (or the portable executable). If you manage to find a clean copy
Assuming you have a Windows 8.1 machine (or a VM) and the file named Win7_Icon_Pack_8.1_Portable_2013.exe : Use Task Manager’s "File > Run New Task"
Run the self-extracting archive to a folder like C:\Custom\Win7Icons . Do not put it in Program Files.