Delphi, Bitmaps, Windows XP, Compatibility

When using Windows XP, bitmaps in a text dfm file are stored in a
different format to those created with Windows NT using the same
screen resolution (1024x768) and number of colors (32 bit).  Likely
this is due to the alpha channel.

That's ok when all developers are using XP, but it's not when there is
a mix of developers on Windows 95, Windows NT and Windows XP.  The
result is that whenever a developer opens a file using different
operating system, the .dfm files containing bitmaps change.  When
these files are under source control, it is a problem when comparing
the differences and performing code reviews, not to mention the source
repository will be getting much larger than it needs to.

Anyone know how to get Delphi under XP to produce bitmaps of the same
format in .dfm files?

XP compatibility modes don't help.

Thanks,
Peter.