Where can I find MakeCert.exe on my Windows 7 computer?

It is used to create a certificate file, a security measure taken to secure web sites, software codes etc.

You find it here

In C:\Program Files\Microsoft SDKs\Windows\v7.0\Bin

or here

In C:\Program Files\Microsoft SDKs\Windows\v6.0A\Bin

Depending on which SDK version you have on your computer you will find in the above directories.