So you have connected to your VirtualCenter server or ESX host and got a big fat annoying Security Warning. Once or twice is fine but after a while you will go NUTS! You can ignore the warning but wouldn't it be great to actually install and use the certificate?! It’s pretty straight forward with XP but Vista needs some care and attention. See below:
Click View Certificate then Install Certificate and then step through the wizard.
For Vista, Be sure to choose Place all certificates in the following store and then Trusted Root Certification Authorities.
After successfully importing the certificate, you will see a dialog box to accept the server’s fingerprint.
Good luck ridding yourself of these annoyances.. :)