Okay with your US Robotice disc. Insert it into the Drive. Dont let the autorun go. Open Computer, not my computer in Vista, and right click on that drive. From there go under the properties menu. Choose the Compatability Tab.
The Properties tab Looks like this. Just click the box for running the application in XP SP2 Mode. The drivers should install fine.
Avast! has been the AntiVirus to use. I have only used the Windows Firewall since i have been unable to find on that will install.
There are drivers out there for the Realtek AC'97 that will work. Just have to download them and install them.
I dont know how well the Steam and iTunes will due. I have had issues running Steam. It starts up the game but then just shuts it down. As for iTunes htere has been reports of problems.
Office and Office 2007 Beta run very well on Vista. I have not personally tried Trillian but i have heard it works just fine.