Normally opt for 64 bit unless there is a reason not to. If you are going to have problems, it usually involves existing USB hardware. This is especially true if RAM is 4Gb or greater. Office and Outlook 2003 will be fine.
Run the upgrade advisor from here click here with your USB devices plugged in and switched on.
A lot of the information will be irrelevant as you are buying a new PC, but you will know what to expect regarding exisitng harware and software