Yes you can install Win7 32bit in your Acer 5745g.
You'll need to do a 'clean install' with a 32bit version. Be sure to back up all your personal files and data first. Make sure you have your Win7 Home Premium license key (25 digit code).
You can get a 32bit version of Win7 here (Windows 7 Home Premium SP1-U ISO English x86 is the file you want).
Download the .iso file and burn it to a DVD and use that as a bootable DVD to install Win7 32bit.