You have an existing version of Microsoft Access and want to try out Access 2010. Well why not download the trial of Office Professional 2010 (600mb) onto one of your least important computers. Once you have done that and made sure you kept your trial registration number from Microsoft, you simply want to make sure that you DON"T REPLACE your older version of Access & Office. For the file location, select a different folder than the one you currently use for Office.
So follow these pictures and only install Access (not Word or Excel or Notes etc).
I have followed this system for 16 years without problems. I use the Access Workbench www.vb123.com/workbench to switch versions ( you will find both versions under the Microsoft Office menu in All Programs )
NOTE: Only edit software and objects in databases that are not needed in earlier versions.