You could do it yourself, but it might be worth trying to reset the registry entries and then re-installing MagicJack before doing a complete Vista wipeout.
The URL that explains the removal of MagicJack is
http://uninstallmagicjack.com/
It shows the registry entries that need to be deleted. Pretty much anything to do with MJ.
Once done, you could try reinstalling your MagicJack. If I recall correctly, that'll just mean plugging the dongle back in.
Best of luck.
If you decide to reinstall Vista, make sure you have your driver CDs ready. Also, the 64 bit version of Vista won't install unsigned drivers unless you do a workaround. Even your wireless will be offline if the driver isn't signed. Basically, that means that you can't even get online to get help installing drivers needed for the rest of your computer.
I had to use an XP computer to help me get Vista 64 going when I upgraded from 32 bit Vista to 64 bit. It can be frustrating.