The simplest way is via their technical support. Microsoft has thousands of tech support representatives worldwide and depending on the software application, the email and/or telephone numbers are different. The best way to locate the right place is to go to the Microsoft web site: www.microsoft.com and select the appropriate support option from the menu.
Free support of some kind is provided on all Microsoft products. In some cases if you need to speak to an actual representative, you may encounter a fee, so have your credit card handy.
The Microsoft people generally try to bend over backwards to help. For example, we had installed the newest version of Microsoft Office 2003 but needed to open an older file that the new 2003 version didn't allow. We left a question in one of the tech support areas for software developers and within 24-hours received not only a very nice reply, but a special link to a downloadable "compatibility patch" that had not yet been released to the public. The patch allowed us to open the old file. If you consider the hundreds of millions of people using their products all over the world, that level of support is extraordinary.