Prasanth In the Command, instead of using VBoxManage.exe , just try giving VBoxManage
eg: VBoxManage modifyvm macos --cpuid 00000001 000106e5 00100800 0098e3fd bfebfbff
(or)
To check whether it is set in path just type "VBoxManage" , if it is in path it will show some list of commands, if its not in path it will show unrecognized!