Hi Peter,
This is an old issue that has come up before. It is actually a problem with the HPBC setup program, not ReefMaster.
What happens is this:
HBPC is a self-extracting zip file, which unpacks the programs required for installation before running them. One of these programs is called "setup.exe", which is obviously a very common name for installation programs.
The HPBC installer tries to unpack this file into your downloads directory, which in this case already contains a file of that name (in your case, it is ReefMaster's installer, but it could be anything).
HBPC ends up writing a file named setup(1).exe (it does not overwrite the existing setup.exe), but then launches setup.exe regardless. Hence, the RM install runs.
You can fix this issue by moving your HBPC download to another directory and then launching it. You can also test that this is what is happening by moving any other program called setup.exe to the same directory as the HBPC installer and running it.
HB have been aware of this for some time (many months) but do not seem to be in a hurry to fix it. I had the problem over a year ago (when I first discovered it); I was convinced there was malware in HBPC because it kept trying to launch the setup for a very dodgy toolbar (Bablyon), which was somehow in my downloads directory..
Matt