I am using Windows and have been given a .cer file. How can I view the details of it?
OpenSSL will allow you to look at it if it is installed on your system.
The format of the .CER file might require that you specify a different encoding format to be explicitly called out.
On Windows systems you can right click the .cer file and select Open. That will then let you view most of the meta data.
On Windows you run Windows certificate manager program using certmgr.msc command in the run window. Then you can import your certificates and view details.