Theoretical maximum compression ratios for executable code and system files (DLLs, EXEs) typically max out at around 60-70% compression at best . This is because system files are already compiled and contain little redundant data.

"Lite" versions often suffer from blue screens of death (BSOD), broken system services, or the inability to run essential applications. 4. Hardware Failure

Obtain a genuine, uncompressed Windows 7 Ultimate 64-bit ISO image.

: Microsoft officially ended support for Windows 7 on January 14, 2020. Using any version of it today leaves you vulnerable to unpatched security exploits. Microsoft Community Hub Authentic Windows 7 Specifications