Save this as a new RegKey. e.g. Del_Pending.reg, then
insert this regkey in your wse-file by using command
Now open your WSE-File with an Texteditor, search for "pending" and find "Root=2" directly under the pending file list. Switch "Root=2" into "Root=194" and save your changes. Now remove pending files "Delete File(s)", e.g.
Delete File(s) %ProgramFilesDIR%\WS_FTP\*.*
mark "Include Sub-Directories" and "Remove Directory Containing Files", klick "OK".
When using this WSE, pending files are removed without rebooting Windows.