From their website FAQs:
I hear no sound when using CyberLink YouCam with my instant messaging software. What can I check?
Navigate to the Volume Control by clicking Start > Programs > Accessories > Entertainment > Volume Control. In the Volume Control window, please check that the system volume is not muted. Also make sure that the volume is set to the correct levels, for both the Master Volume, as well as the Wave volume.
What are the minimum system requirements for CyberLink YouCam?
YouCam 5 Minimum System Requirements
OS: Windows 7 / Vista / XP (with DirectX 9 or above).
Memory: 512 MB (1 GB recommended).
CPU: Intel Pentium D 3.0 GHz. / AMD Athlon 64 3200+ or above.
HDD Space: 1 GB required.
VGA Card: Intel 945 (Independent graphics card recommended).
Device: Webcam (built-in or external USB).
Instant messaging software with video communication functions, such as Windows Live Messenger, Skype, Yahoo Messenger, AOL Instant Messenger.
Windows Internet Explorer 7 or above to use the Face Login sign in to web sites feature.
Note: To ensure you can enjoy all the features in CyberLink YouCam, make sure your computer meets or exceeds the minimum system requirements.
If you don't have one, here's a link to download the manual:
Still need help? Here's a link to their website's technical support: