Vista doesn't seem to like Vonage V-Phone. Here's the best way to get it to work:

1) Using Windows Explorer navigate to the USN stick's drive (ex: Drive G)
2) Open the Vonage directory
(If you don't see it, select Tools, Folder Options, then click the View tab, select SHOW HIDDEN FILES AND FOLDERS, then click OK)
3) Right click on the 'autodown' file and select CREATE SHORTCUT.
4) Right click on the new shortcut, select CUT
5) Navigate back up to the main directory of the USB Stick (ex: G
6) Right click and select PASTE
7) Rename it so it is simply 'Run Vonage Talk'
8) Right click on the new 'Run Vonage Talk' file, select PROPERTIES
9) Select the COMPATIBILITY tab
10) If you are NOT admin, select SHOW SETTINGS FOR ALL USERS (If you are admin, skip this step - step 10 only)
11) Check the box for "Run this program in compatibility mode for"
12) Select Windows XP
13) Check the box under Privelege Level for 'Run this Program as Administrator'
14) Select Apply
15) Select OK
16) Now doubleclick the 'Run Vonage Talk' file and Vonage V-Phone will run.