You should be able to purchase an Access 2007 upgrade from one of the retailers for a reasonable price.
I highly recommend against running multiple versions of Office Application installations as these quite often share portions of the core codes. When you start mixing the versions (acc2003 here, word2007 there, and yet Something2010 over yonder) the installations become unstable.
They tried that in my Wife's office and the entire thing crashed their server within a short period, twice, before someone finally took notice of what was installed. Purchased the most recent version of Office and upgraded the enterprise. Once done, not a single crash.
Something to keep in mind: when you upgrade the Office software, with Access, occasionally there are issues with using the older *.mdb files. The easy fix is to just create a new mdb file within the new version of office and import the contents of the old mdb file.
IMHO: You should also SKIP ACC/OFFICE2007 and move to 2010. There were a lot of bug fixes and the Ribbon is much improved in 2010.