Hmm... bit weird. 52% usage? When i'm on the internet, listening to music, and chatting to mates, i get about 13% usage, so its a bit weird its going as high as that!
Could it be your internet connection though?
If its a slow connection, of course, you'll get a slower speed and so pages will take longer to load and commands won't be delt with straight away.
Turn off the internet and put music on for example, and check the percentage. Then turn the internet back on and check the usage. Whats it like with music playing, but just not the internet?
I have a feeling maybe your internet connection itself is using alot of resources. This could be because maybe your using an in-built modem of some kind that came with your motherboard?
If your not happy with the results from this, call your ISP. They'll hopefully be able to issue out a card that will fit into a PCI port (or find a compatable one) and use your connection.
A card in a PCI slot you see meant for the job won't use precious CPU time while surfing.
I hope this helps