I recently bout an HP Pavillion 15, with an AMD A8 CPU, AMD Radeon 8600 series GPU, 12GB RAM, and 1 TB hard drive. It did have Win8.1 on it originally, but I overwrote it with Linux.

My problem is this:
After running the necessary updates, and installing the needed AMD drivers via the Additional Software tab, with either moving the cursor, or even trying to click on something on the dock, I get a desktop hangup.
It tends to hang up for about 30 seconds or so, and then it appears to run rather slow, as if 'laggy'. This problem, as you could guess, makes Ubuntu rather unusable, as it happens quite frequently.

Would anyone be able to offer me some advice as to how I can fix this and get Ubuntu running smoothly?