A legitimate, clean file typically occupies:
Windows 7 Ultimate 64-Bit "Highly Compressed": The 10MB Myth vs. Reality Windows 7 Ultimate 64 Bit Highly Compressed 10mb --BEST
If you downloaded such a file, delete it immediately and run a full antivirus scan. Never mount or execute unknown small OS archives. A legitimate, clean file typically occupies: Windows 7
Even with the most advanced compression tools available, a 3.5 GB Windows ISO will rarely compress down to less than 2.5 GB. To shrink 3,500 MB down to 10 MB would require a compression ratio of roughly . This is technically impossible for an operating system of this complexity. Windows 7 Ultimate 64 Bit Highly Compressed 10mb --BEST