You may need to up your Power Supply to 400 Watts to handle the the 4600 series, the 4650 may require as much as 425 Watts. I just spoke to an accredited specialist about the necessary power supply, Something to think about.
Uninstalling the old driver is right on the money. I have a question myself: If I was to download the latest driver, what is the start up disk that comes with the Vision Tek 4650 all about....elusive?
First, this thread is almost two months old. No need to respond to it. If the OP was coming back he would have already.
Second, any "specialist" that told you a HD 4650 needs a 425w power supply is an idiot. As you can see in this benchmark The entire system with an HD 4650 uses a maximum of 178 watts.http://www.tomshardware.com/reviews/radeon-4650-agp,2383-9.html
An HD 4650 will run fine with a very small stock power supply.
Third, the driver disk contains a driver for those without internet access. Those with internet access should obviously download and use the newest driver available for their card.