Determining os version from an evidence image -
One of the first steps an examiners will need to carry out once they have an evidence image is to log system metadata, including OS version and patch level. This may be of particular importance if the image in question is from a machine that is suspected of having been compromised.
Windows
Windows 95/98/ME
Establish the boot volume, verify that it is a FAT file system, and locate the hidden text file \MSDOS.SYS. Locate the [Options]WinVer parameter:
WinVer OS 
4.00.0950	Windows 95	
4.00.1111	Windows 95 OSR2	
4.03.1212	Windows 95 OSR2.1	
4.03.1214	Windows 95 OSR2.5	
4.10.1998	Windows 98	
4.10.2222	Windows 98 SE	
4.90.3000	Windows ME	
Alternatively, establish WinDir ([Paths]WinDir in \MSDOS.SYS), locate the %WINDIR%\SYSTEM.DAT registry file. Next, look up the registry key Software\Microsoft\Windows\CurrentVersion\, and values Version and VersionNumber. (Backup copies of SYSTEM.DAT may be found in .CAB files in %WINDIR%\SYSBCKUP.)
Windows NT4
Windows 2000, XP, 2003, Vista
Information about a running system can be displayed using the command `ver` (and `systeminfo` on some systems).
During a forensic examination, information regarding the version of Windows can be found in a number of places. For example, by default, the Windows directory on Windows XP is "C:\Windows", where on Windows NT and 2000, it was "C:\Winnt". This is not definitive, however, because this directory name is easily modified during installation.
Determining the version of Windows from the Software Registry Hive file - navigate to the Microsoft\Windows NT\CurrentVersion key, and examine the values beneath the key; specifically, values such as ProductName, CSDVersion, ProductId (if available), BuildLab, and on Vista, BuildLabEx.
Determining the version of Windows from file version information - locate the file %WinDir%\system32\ntoskrnl.exe and review the file version information/strings from the resource section of the PE file. You can view this information with a hex editor, or extract it using a variety of means. There is a Perl module (Win32::File::VersionInfo) that will allow you to extract this information, and the Perl script kern.pl illustrates a platform independent means of examining the PE header and ultimately locating the file version information.
In order to determine the difference between Windows XP Professional and Home versions, look for the %WinDir%\system32\prodspec.ini file; it contains information regarding the Product type (either XP Pro or Home). Another way to do this is to look at Microsoft Product Code (first 5 digits of Product ID). Some of these values:
Value (MPC) Version 
55034	Windows XP Professional English	
55683	Windows XP Professional Russian	
55681	Windows XP Home Edition Russian	
Other
Windows 2008
Windows 7
Windows 8
Windows CE, Mobile
Different editions per version?
Unix/Linux
Information about a running system, including the kernel version, can be displayed using the command `uname -a`. However, this is not much good if you performing dead analysis on a disk image.
Linux
A number of Linux distributions create a file in /etc to identify the release or version installed.
/etc/issue /etc/issue.net 
Distro Tag 
Red Hat	/etc/redhat-release	
Debian	/etc/debian-version	
(Open) Solaris
Free/Net/OpenBSD
A first indicator of the presence of a BSDs operating system is the partition table on a MBR-partitioned disk:
OS Partition type 
FreeBSD	FreeBSD (0xA5)	
OpenBSD	OpenBSD (0xA6)	
NetBSD	NetBSD (0xA9)	
		
You can get the release and version of BSDs operating system inside the kernel images, even with only a disk image.
OS Kernel path 
FreeBSD	/boot/kernel/kernel	
OpenBSD	/bsd	
NetBSD	/netbsd	
		
You can use strings and grep tools to find this information with strings kernel_path | grep os_name. (e.g.: strings /bsd | grep OpenBSD)
AIX
HP/UX
Other
BSDI
Other
Plan9
QNX RTOS
OS2
MacOS-X/IOS
DOS