Windows Vista may have new features for mobile computers, but the operating system itself is becoming considerably less portable. Under changes to Microsoft's licensing terms, buyers of retail copies of Vista will be able to <A HREF="http://news.zdnet.com/2100-9590_22-6126379.html">transfer their software to a new machine only once.</A> If they want to move their software a second time, they will have to buy a new copy of the operating system. In the past, those who bought a retail copy of Windows needed to uninstall it from any machine before moving it to another machine, but there was no limit to how many times this could be done.