It doesn't matter whether you have the HD4650 AGP or PCI-E. I have a HD4650 AGP card. One of many cards.LOL. For your card you need to go into "Testing" and install the ATi 9x driver. that should do the trick. It works for me. As to your webcam problem, you have two choices: 1). open synaptic and search.."quickcam pro". You will see two boxes, click either one and it will install as a dependency the required kernel for it. It works great. I have a QuickCam Pro. working just as designed.
Option 2) When in testing, you could update your kernel to 22.214.171.124 at the same time you update your ATi driver. With this Kernel your webcam will work without any other repo adds.
For a complete novice, the best choice would be to load the quickcam install first, then reboot. At post select the bottom new kernel 126.96.36.199. Then go into "Testing" and load the 9x driver. To get into testing, after synaptic comes up, at the top click on repository. when the window opens, highlight the box that is checked, if it's (belnet) change it to one of the Indiana sites. Only have ONE box checked ever. highlight and go down to "Section" type in: testing. Follow the prompts and then scroll down to ati 9x. Install and follow the prompts.
It would help a bit if we knew if you were in KDE 3 or 4 or GNOME.