Yes. If you use a custom install, you can install Office 2003 as well.
(I personally did it in the opposite order, but it should work.)
There are some issues. When you switch to Access 2007 after using 2003, it
runs a reinstallation which takes longer than rebooting the computer. When
you switch to A2003, it also runs a reinstallation, but not quite that long.
It's annoying enough to make you think twice before switching versions.
Even more siginficiantly, I am starting to lose the Help in Access 2003. If
I highlight a keyword in the VBA window and press F1, I get a competely
blank help screen now. At this stage, the help index still works, but in the
beta it gradually got worse, so I am expecting to gradually lose more and
more of the help in all previous versions of Windows. (Presumably this has
to do with the tens of thousands of registry entries that get overwritten
each time you switch versions.)
More info:
Converting to Access 2007
at:
http://allenbrowne.com/Access2007.html