The correct function name is SetPriorityClass() not
SetProcessPriorityClass().
NSSM can set the priority class of the managed application. NSSM will look in\r
the registry under HKLM\SYSTEM\CurrentControlSet\Services\<service>\Parameters\r
for the REG_DWORD entry AppPriority. Valid values correspond to arguments to\r
-SetProcessPriorityClass(). If AppPriority() is missing or invalid the\r
+SetPriorityClass(). If AppPriority() is missing or invalid the\r
application will be launched with normal priority.\r
\r
\r