UltraVNC 1.2.1.7 service fails to stop

Root cause is likely a duplicate of CORE-13233, but behavior is a bit different,
so let's try to help without confusing that other issue.

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UltraVNC 1.2.1.7: ultravnc 1217 X86 setup

Windows XP:
sc stop reports STOP_PENDING,
then STOPPED after 1-2 seconds this service takes to complete unloading.

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reactos-bootcdregtest-0.4.8-dev-1086-gd1265b9-x86-gcc-lin-dbg.iso
+ Windows XP mfc42.dll in install directory, as required by UVnc setup. (NB: The latter seems written with Delphi.)

1. Run Setup.
1r1. Lots of visual glitches, but out of scope of this issue.
1r2. Service is automatically started, though I asked not to. (Same on WXP: installer "issue".)

2. sc stop uvnc_service.
2r1. It reports STOP_PENDING and CHECKPOINT: 0, forever,
2r2. winvnc.exe remains listed in Task Manager, with CPU=0%.
2r3. Scm does not allow any actions.
2r4. Event Viewer only reports that the Stop command was successfully sent. Later Stopped state log is missing.

I've got a full log, but I'll double-check it before posting it...