You can install Lightroom on two computers if you own them both. You can not use both at the same time.
I'm not sure what "insert" you are talking about, but as said above a perpetual license is good for installation on two computers. If the old computer is still functional, you can either uninstall LR5 from it or consider a new computer as the second installation. If the old computer is not functional and will never be used again, then LR is not functional and this is equivalent to its having been uninstalled.