1. run as localsystem user
2. give the variable "drivename" the drive letter whatever you want to check. For example: if you want to check the "C" drive for minimum space then give "drivename" value as
"C" or if you want to check multiple drive then give "C D" or "C D E" like this. Just give space between the drive letters if you want to check multiple drive.
3. give the variable "minimumFreespace" the minimum space you want to check and give the variable "unitMeasurement" the unit you want to check. for example if you want to check for 10gb free space then just give the variable "minimumFreespace" the value 10 and give the variable "unitMeasurement" the value "gb". you can give"kb" or "mb" or "gb" in unitMeasurement.
for your understanding look at the below example,
drivename = "C D"
minimumFreespace = 10
unitMeasurement = "gb"
the above example will search for 10 free space for both the drives C and D. if you want to check for 100mb then just change the "minimumFreespace" to 100 and change the "unitMeasurement" to mb.
do not give decimal numbers like 10.2 or 50.4 in the variable "minimumFreespace". always give the natural numbers.