[legion]

I got Office 2007 for $20 through a program with my employer. My license allows me to install it on up to 3 PCs. Can you check to see if your employer offers a similar program?

Microsoft literally has hundreds of different versions of its EULA for various products. I assume you have the retail EULA on everything. (Which generally allows you to install the product on one PC.)

If you have a valid license for Office 2003 and it is not being used on any other PCs--you have at least cleared the potential legal issues. However, going backwards a version might prove technically challenging. Your best bet would be to completely uninstall Office 2007, then install Office 2003. Even then, you may still have problems.