What are your PC Specs? Just because you have a cable modem, it doesnt necessarily mean, that your pages are gonna load faster. Having a good video card, decent amount of RAM(memory, about 512, should be sufficient for viewing web pages), and a good proccessor, is alot of what make a computer go. As Sneak stated, it could also be do to the fact that we cable users, run slower during "peak hours," which is around 12pm-10pm. Other than that, you should be fine.
ON the other hand, Ghostly is also correct. Having a bunch of useless shit on your computer doesnt help any. You should always keep your hard drive about 50-60% free. When you start to go over this, it tends to slow down, because it uses too much memory.