Hello Bent, are you using RealBand or RealBand64?

An error about not being able to select the input device could be because of not having a microphone. Or if your computer has a built in microphone, it could have to do with the system being set on the wrong sampling rate.

Right click on the Windows Start menu and choose Run, then enter "control mmsys.cpl sounds" and press OK. This will open up the Windows Sound control panel.

Under the Playback tab, choose your default audio device (with the Green checkmark), then click on Properties. Go to the Advanced tab and choose 16-bit 44100 Hz (CD Quality) and click OK. If there is only the option of 24-bit 44100 Hz (Studio Quality), choose that instead. While we're here, uncheck the option to "Allow applications to take exclusive control of this device".

Next, do the same on the Recording tab with the device that has the Green checkbox. Click Properties, go to the Advanced tab, and choose 16-bit 44100 Hz (CD Quality) and click OK. If there is only the option of 24-bit 44100 Hz (Studio Quality), choose that instead. While we're here, uncheck the option to "Allow applications to take exclusive control of this device".

Once that is done, click OK on the Sound window, then go back to RealBand and make sure it is working.

Best,
Chantelle