Hi,
Thank you for posting in Microsoft Community.
Since you have installed 32 bit of Office 2007, you may not be able to install 64 bit of Office 2013 preview. Uninstall Office 2013 preview completely from the system, download a 32 bit of Office 2013 preview, save it on the system and run the setup
from the saved location and check if it helps.
You may refer the link mentioned below and check the section Method 1: Uninstall Office 2013 Preview Click-to-Run suites with a Microsoft troubleshooter too to uninstall the traces of Office 2013 installed on the system:
http://support.microsoft.com/kb/2739501
Note: If Windows 7 is a 64 bit operating system then download and save the fixit tool on the system and then try to run the file from the system.
Once the Uninstallation is complete reboot the system.
You may download Office 2013 preview from the link mentioned below and check if it helps:
http://www.microsoft.com/office/preview/en
Note: Ensure to save the setup file on the system and then run the setup from the saved location.
I hope the above suggestions helps to resolve your issue. If you need any further assistance reply and we will be glad to assist you.
Thanks you.