The .7z extension indicates the files are compressed using 7-Zip, which is the standard archival tool for these projects. Installation Prerequisites
Version is widely regarded in the community as a stable and "popular" baseline for Windows 2000 modernization. W2K Extended Kernel 3.0e.7z
It is often preferred over later, more "fragile" versions like 3.1j, which have been reported to cause blue screen errors (BSOD) if prerequisites aren't met perfectly. more "fragile" versions like 3.1j
It adds missing Windows API functions that programs often require to launch, which are natively absent in Windows 2000. W2K Extended Kernel 3.0e.7z