Should I Use Access 64-bit? In Microsoft's own words, not unless you need 64-bit Excel or Project:
(source: Microsoft White Paper: Improving the Reach and Manageability of Microsoft Access 2010 Database Applications with Microsoft Access Services)
Multi-Access Installations Our testing has shown that you cannot
have a 32-bit and 64-bit version of Microsoft Office installed on
the same machine. The reason is likely related to common
library conflicts. Whatever the reason, it is important to
note that you cannot have Microsoft Office 64-bit installed on a
machine that also has Access 2007 or lower installed, which are only
in 32-bit form.
Developing Access Databases with API
Calls If you have a current
Access database that employs Windows API calls, you will need to
conditional compilation attributes to your applications for 32-bit and 64-bit
Office users. To support Office 2010 64-bit users of your application, you
will need to preface your "Function" and "Sub" declarations with "PtrSafe"
for your project to compile.
If you aren't sure what a
Windows API call looks like, we've placed a snapshot below:
You don't have to install Office 2010 64-bit if you have a 64-bit
processor. While you may lose some performance, the 32-bit
version of Office 2010 will work just fine with a 64-bit processor.