: This denotes that the build is based on the original release of Windows 7, without any service packs applied. Service packs are updates that include a collection of fixes, updates, and improvements to the operating system.
: 6.1.7600.16385. The "6.1" refers to the NT kernel version, and "7600" is the build number. windows 7 sp0 x64 build 617600 full version link
This specific build represents the original, "Service Pack 0" (SP0) version of Windows 7 before any major service packs were applied. Official Version String : 6.1.7600.16385. Release Date : This denotes that the build is based