[kovidgoyal]

I tried adding the following as the last entries before product

                <InstallExecuteSequence>
                    <FileCost Suppress="yes" />
                </InstallExecuteSequence>
                <InstallUISequence>
                    <FileCost Suppress="yes" />
                </InstallUISequence>
                <AdminExecuteSequence>
                    <FileCost Suppress="yes" />
                </AdminExecuteSequence>
                <AdminUISequence>
                    <FileCost Suppress="yes" />
                </AdminUISequence>

I got the following warnings from WiX

C:\cygwin\home\kovid\build\calibre\build\wix\calibre.wxs(4707) : warning LGHT1008 : The action 'FileCost' in the InstallExecuteSequence table is being suppressed.
C:\cygwin\home\kovid\build\calibre\build\wix\calibre.wxs(4710) : warning LGHT1008 : The action 'FileCost' in the InstallUISequence table is being suppressed.
C:\cygwin\home\kovid\build\calibre\build\wix\calibre.wxs(4713) : warning LGHT1008 : The action 'FileCost' in the AdminExecuteSequence table is being suppressed.
C:\cygwin\home\kovid\build\calibre\build\wix\calibre.wxs(4716) : warning LGHT1008 : The action 'FileCost' in the AdminUISequence table is being suppressed.

The checking space requirements action seems to have decreased in duration (took about 30secs as opposed to a couple of minutes). I would have thought it would go down to almost zero, but...

I'll leave it in, hopefully there wont be any nasty side effects. In a system as byzantine as windows installer, how is one supposed to know if there are going to be side-effects?