This problem is due to 'HydraStudio' not being able to find the C compiler.  This can be fixed by making an entry into a file located at "C:\Program Files\Querix\hstudio" (or where you have installed 'HydraStudio' to), the file will be named 'Microsoft Visual C++.env'.  The last entry in this file is labeled 'PREBUILD=', the file path of the vcvars file should go here.

The vcvars file is located within your Visual Studio installation and is a file needed to use the C compiler.

An example of the file path is: 'C:\PROGRA~1\MICROS~1.NET\Vc7\\bin\vcvars32', please bare in mind that you will need to use the MS DOS names for the directories so it will be 'PROGRA~1' instead of 'Program Files'.

Once you have put the file path into the 'PREBUILD=' entry save the file and compile the program again. If the new entry points to the vcvars file you will find that the errors stop.