When I installed Vista on my home computer I noticed that my phone would work with the new sync update for Vista. Here's the work around to get a ppc4100 Audiovox phone to work with Windows Vista.

1) Make sure your Mobile Device/PDA is unplugged.
2) start RegEdit and add a key called “WHOS” or "WHOIS" to HKEY_LOCAL_MACHINE/Software/Microsoft. Close regedit.
3) Plug your Mobile Device/PDA wait till the PDA syncs .
4) Start Windows Update, and "Check updates" you should now see a 7.* mb update waiting. Install this.
5) Go to Control Panel > Windows Mobile Device Center and you should be seeing Your device connecting and waiting to be configure.

You can now sync outlook/contacts/tasks or sync pictures/movies or close this and Start installing PDA Applications which are available only in .exe format. I installed couple of such OLD setups and even if this is Vista rc1 that too x64bit edition they installed smoothly Cool or what!.