Select a different math font in Microsoft Word

While not being a universal solution (Not every font is suitable for this solution), the alternate font XITS Math provides a font that works with the equation editor out of the box. Here is what it's going to look like in the end (You will notice the font looks similar to the font "Times"):

1. Setting XITS Math as a default font for new equations

1. Head to the Downloads page of xits-math. Select the .zip version of the latest release, as demonstrated below:

   

2. Unzip the .otf fonts from the archive.

   

3. Install all the font files by selecting them in the Windows Explorer, right-clicking and Selecting "Install".

4. Open Word and create a new equation. Then select the little "additional settings" corner.

   

5. In the menu, change the "Default font" to "XITS Math".

   

6. In order for the changes to take effect, you will have to create a new equation environment (the current one will not be changed).

   

2. Changing existing equations to XITS Math

You need to have the fonts for XITS Math installed first. If you have not done so yet, please complete steps 1–3 of the section "Setting XITS Math as a default font for new equations" (above).

1. If you want to change only one equation environment, just position your cursor inside it. If you want to change multiple environments, you can them by selecting one after the other whilst holding Ctrl.

2. In the "Home" tab, select the font "XITS Math" by choosing it from the list or typing its name into the box.

   

Support for other fonts than XITS Math

The use of XITS Math was just an example chosen for this answer. There are probably more fonts that qualify as math fonts, but I have not found more. Please edit this answer or comment if you have found a font that could be added here.

An addition to the answer by RAnders00, there is a very quick way to change all of the fonts of existing equations using the advanced find.

"Advanced Find" allows you to search by format as well as for text content.

Leave the "Find what" field blank, and choose "Format > Font… " to select the font you want to find.

Then click the "Replace" tab, and do the same to choose the font you want to replace with.

Then click "Replace All", and it will replace all occurrences of the font you chose.