Only administrators have permission to add, remove, or configure server software during a terminal service remote session.’

I wanted to install an application on one of my oldest windows 2003  terminal servers and suddenly got an error messag

“Only administrators have permission to add, remove, or configure server software during a terminal service remote session.'”

I found out that by adding the follwing registry this problem got solved. Strange.. it worked for years this way…

Registry Key:  HKEY_LOCAL_MACHINE \Software \Policies \Microsoft \Windows \Installer

Add Value name: EnableAdminTSRemote

Date Type: REG_DWORD

Value data:1

Base: Hexadecimal