There are basically two ways of backing up software:
Firstly there are system images, they back up your whole computer's state and backup the software you have installed at the time of making the image. A system image can be restored from after a disaster to take your computer back to an older state with all the software installed. A system image also backs up all the deafults with which you like the software to be set up. On some windows version there is a system imaging tool built into control panel.
Secondly you can sometimes just back up the installer exe files like you would back up any other file, certainly for offline installers (ones which contain everything needed for installation, as opposed to online installers which start downloading the things needed for installation when you run them) you can copy and paste them onto a usb or burn them onto a cd-rw as you would any other file. If they are offline installers they should then be able to run and install the program on any machine you copy the file onto and then run the file on. For online installers the installer will only be able to install onto machnes which are connected to the internet at the time you run the installer and for online installers they only continue to work if the software is till available online. Offline installers will still work even if the software is no longer avilable for download anywhere, so are very helpful to keep copies of if you use old software (perhaps where you still use an old version rather than the latest version for some sort of compatbilitity reasons). To make this kind of backup you need to make sure to download the installer exe file and ave it in a folder somewhere, if you've already deleted the installer exe file (or ran it straight away rather than svaing it) then it is too late to do this unless you download the program again and store a copy of it's installer then. Note that backing up the files ofnthe program after installation (it's files and folders under C:\programfiles\ is generally useless, you can't install a program just by copying these into the same folder on another machine, if you want to backup a program by a means other than a system image you will need to backup it's installer file.
Edited by rp88, 08 June 2015 - 01:56 PM.
Back on this site, for a while anyway, been so busy the last year.
My systems:2 laptops, intel i3 processors, windows 8.1 installed on the hard-drive and linux mint 17.3 MATE installed to USB