Cannot find comport? Windows, GUI, accelerometer

Hello, i'm currently trying to run a code but cannot seem to find any open ports. Here is the error i receive...

Error using serial/fopen (line 72)
Open failed: Port: COM4 is not available. No ports are available.
Use INSTRFIND to determine if other instrument objects are connected to
the requested device.

help is much appreciated

[Jan]

Without seeing the code, we cannot guess what's going wrong.