When you open ahp, the instructions send you to the cm11a setup screen. And that screen says that if you are using usb, you are supposed to select disabled for the com port.
Do not select disabled for the COM port.
I have not been able to use the disk that came with the adapter - it has many folders but no instructions.
When Vista says it found new hardware, does it ask for drivers?
How can I find out what has com3 now?
Nothing has it since you have no COM ports (other than the usb<->serial adapter) - those are imaginary. It would be helpful to know whether they existed before you tried the adapter.
My testing with Vista was limited (I had my granddaughter's PC to clean up after she clicked on one of those scary virus messages that kidnap your machine and hold it for ransom.) but I had no issues whatsoever with a Y-105 adapter.
I would unplug the adapter, remove all of the phantom com ports, reboot, see if the phantom ports are gone (Device Manager) and, if they are, insert the adapter anew to start over.
I'm wondering whether the CM15A problems were caused by problems on the PC, itself. Where do you live? Perhaps a nearby expert can test the CM15A if you mail it to them.