The point is not that you need these utilities, but they are very well annotated (even including source code with the downloads) and contain some information you may be able to use.
The links are to the "as posted" articles about the utilities, which require paging through multiple "more" buttons; but if you click on the "printable" button, you get the whole article in connected form that can be printed or (my usual) saved to a scratch file.
Startup Cop, in particular, describes the registry keys and other files where information can "boot" itself, and gives an unusually intelligible description of Windows startup processes. If you use the list of functions and files as a guide, you should be able to find any "reset" clinkers that may be on your machine.
There is the possibility that each new net send message you get contains the turn-on command, but disabling the net send utility should block that unless you're on the net or otherwise running your machine logged on with Administrator privileges.
There is probably enough information to be helpful in the linked articles. I don't know whether downloading the files gets additional detail. You can download without installing them, if you want; and you should be able to unzip any "readme" files without installation, although I haven't checked that out for these two utilities.