SIr.
I have 2 PCs. One is a laptop, another is a desktop. I was earlier using DYNU for my laptop and it was navigating my domain to my laptop.
Today I added one more domain and installed and linked another ip update client on desktop. Now when I open different domains, i randomly see any device. Sometimes one domain points to laptop, 5 minutes later, it points to the desktop.

Please suggest a way to resolve it !

1. Please make sure that the 2 devices are getting static internal IP addresses.

2. Set up port forwarding for both devices in the router to be accessed on different ports. For example:

laptop external IP:80 -> internal IP:80
desktop external IP:81 -> internal IP:80

Then you can use yourdomain.com to access the laptop and yourdomain.com:81 to access the desktop.