When you open the Control Panel > Programs and Features applet, you may have noticed in Windows 7 that in some cases the sizes of the installed programs are not being displayed.
A question which may arise in one’s mind is that how does the Programs and Features get the size and other information?
A program can add some properties to its registration to avoid a lot of this guessing. It can set an EstimatedSize property to avoid making Programs and Features guess how big the program is.
But if a program omits all of these hints, Windows is forced to guess, and the guess that Programs and Features ends up making can often be ridiculously wide of the mark due to coincidental word matches. This has been very nicely explained at MSDN blogs.
It is also found that the EstimatedSize property (DWORD value) does not support size of 4 GB or more.
In Windows 7, when the installer is not an MSI, the Control Panel does not display the Size. It only looks for the EstimatedSize value. If it is there, the size gets mentioned. If not, the size column is left blank, explains MSDN Blogs.
So, non-MSI installers will have to start writing that value, if they want the program size to be displayed!