InstallAware

it is estimated as size of $TARGETDIR$ folder defined in installer. How to pass only to ARP another path, in my case it is $TARGETDIR$ subfolder '$TARGETDIR$\\ComponentName' ?

Actually, this is estimated internally by Windows Installer. I don't think it has anything to do with $TARGETDIR$.

You can hard-code your own size if you wish, by directly writing to the registry.

But the size displayed is exactly as TARGETDIR folder size...
Do you know where in registry is this size stored?

A quick Google search reveals this location to be:

HKLM (for ALLUSERS=TRUE)
HKCU (for ALLUSERS=FALSE)

\\Software\\Microsoft\\Windows\\CurrentVersion\\Uninstall\\$TITLE$
EstimatedSize (INTEGER)= $MYSIZE$

and quick test on registry editor - and it doesn't work. Either on 2k or Xp. ARP displays the same value all the time.
This was the reason of my previous post.

You may have modified the wrong area of the registry. You can search for this field in other ARP entries and correlate your findings.

This is exactly what I've done before. I've changed Microsoft components size and it looks, ARP is not using EstimatedSize anymore.