I uninstalled 3CX Assistant 9 from a Windows 7 SP1 Professional machine a couple months ago. Suddenly this past weekend, the "3CXPSTAPI.tsp_unloaded" module started crashing TAPI (error at bottom of post), and whenever it crashed, it brought down several other services and caused Windows to lose authentication. I've posted the details here: Windows 7 Issues after 3CX Assistant Uninstalled That post includes updated manual uninstall instructions. The most critical step is to run this command: regsvr32 /u C:\Windows\System32\3CXPSTAPI.tsp I hope that helps anyone else experiencing this problem. I also hope that 3CX has updated the uninstall to really uninstall!