I have two OSs Windows XP and 7.How can i use google chrome on both by installing in any one?

You can't. Programs have installers for a reason- they do a bit more than just drop a file on your hard drive. Programs have to register shared components with the operating system, and install some core settings in a global settings file called the registry. When you install a program, it can only see whatever OS you are currently using- there's no way for it to find the other OS.