Maybe to someone it helps...get folder size in windows with powershell
1.Edit nxagentd.conf and paste next
ExternalParameter = FolderSize(*):powershell.exe ( Get-ChildItem $1 -Recurse -Force | Measure-Object -Property Length -Sum ).Sum / 1KB or /1MB if you want Mbytes, /1GB etc....
2.Restart agent.
3.Add Parameter to your node.
Enjoy. 