I just bought an HP Pavilion 23 PC with windows 8.1. I am using InDesign CS4 on a PC with Windows 7. Does Adobe support Windows 8.1 and how do I get it installed on my new computer?

Bobpineo Windows 8 was not in existence during the time period which Creative Suite 4 was available.  You are certainly welcome to try installing and utilizing the software under Windows 8.1.

If you need a fresh copy of the installation files then you can download them from Download CS4 products.