I recently bought an hardware device which use your virtual serial ports program, and faced an installation issue on my new computer.
Actually, the installation of the software package provided by the manufacturer of this device was hanging just after the closing of vbsetup.exe. I had to kill the install process, and noticed in the task manager an instance of regVSP.exe, which was hung. Of course, I couldn't create any virtual serial port, and my device was totally useless :-(
After several hours examination of logs provided by RegMon and FileMon, it appeared that the presence of u3dapi10.dll (installed by TortoiseCVS, and located in the CVSNT directory) was the cause of this malfunction ! Renaming it (u3dapi10.dll.xxx for example) did the trick !
You can rename it back to its original name after the install, but you must keep in mind you'll have to do it again when installing an updated version, or for uninstallation.
To be honest, I can't say exactly what is happening (I'm sure the Eltima developers could explain it more precisely), but I just wanted to inform you abt that, considering the hours I spent on it ;-)
FYI, I'm using XP Home SP3.