It is said that Upgrading is a No-No, more so when you are going from 32 bits to 64bits... it is always recommended to install a Fresh OS to avoid compatibility issues.
I have found that 64 bit is more prone to ask for better or newer drivers and it requires that sound/video and now monitor drivers be 64 bit as well.
Now, don't go believing what I am saying here, I am not a PC guru by any stretch of the imagination, this is just my Personal Opinion since switching from 32 bit XP to now Dual Booting with VISTA ULTIMATE 64 & WIN 7 ULTIMATE 64.
All I can tell you is that I play a lot of games (Single Player/Campaign Type ONLY!!!) so, if your issue is with the ONline or Internet... I can not help you.
Being said that, as soon as I got to Vista/Win 7 64 I started having issues with video, did everything I could to fix it, uninstall video drivers, use a sweeper, reinstall newer drivers, older ones, etc, etc... you name it, I did it. What fixed this for me was the need to also Update my Monitor driver (I was using an old 32 bit driver that wasn't even compatible with Vista 32, let alone 64 bit). I end up having to download a 64 driver from a newer model LCD than mine but it worked a treat... been happy ever since.
Again, this may not even be close to solving your problem, just trying to give you another thing to check. I don't know anything about ATI or AMD so I don't know whether your CPU is capable or enough for the games you want to play, I am sure others would have mentioned it if it wasn't though.
So far, nobody has recommended you to update your drivers because you said that you already did. Now, History has told me that there are plenty of people that say they have installed newer drivers and it turns out they never really did or they did it wrong so... if you don't mind, can you give us the driver versions and tell us how you went ahead and did the updates? You may find this tedious and even stupid but, it may save you a lot of time in the long run