🚀 go-pugleaf

I don't think you need to upgrade to 3.0, although with Vista being certain of anything is dangerous.

Here's what I would do. First close AA 1.5, then....
Go to Vista's Control Panel-> Sound, choose the Recording tab and check that you have some inputs showing and enabled and also have little level meters shown to the right of the listed inputs. There are various options with these inputs - they may say "Working", "Disabled", "Not plugged in" and so on. If you don't see inputs, right click on the blank space in the Sound panel and make sure you are set to show Disabled and Disconnected devices.
In the panel, if you see no meters, they may appear if you randomly select and deselect inputs.

Then start AA 1.5 and go to Options-> Device properties->Wave In and make sure something like Realtek is selected and Use in Edit View and Try as WDM are ticked. Then open Device Order in the Options menu and make sure that the Realtek device is at the top of the list in the Recording devices tab.

It all then ought to work. Note that you may need to have something plugged into an input to make it visible to Vista and hence AA.

Let us know what happens.