I think my PC has a Ramnit infection somewhere

The problem is that I entered on a cached page and accessed the option of viewing the content in text only, and that’s because I couldn’t see it. I scanned the full content version + the cached one online with virustotal and didn’t find any threat. When I entered the only text option from the cached version the toolbar of Norton showed me the page was marked with orange color, the Caution level of risk. The online scanner (virustotal) showed me that only an antivirus detected malicious content in it. I decided to fully scan the system + to activate NPE including the downloading and the putting the Ramnit removal tool from Symantec in operation. Any of these scans didn’t find this threat! I decided (before downloading the removal tool) to go further in this Norton analysis and it found 4 threats. Then I looked more carefully and didn’t saw the full link just the beginning ( web cache googleusercontent or something). All the four threats were in fact one (Ramnit!html) and were pointing to a really infected website ( of a University) which had many viruses (colour red). This evaluation gives me the impression that as long as a cached website is virused the root (web cache googleusercontent only, meaning that nothing is after the .com extension) is the same way. I am uncertain, please someone explain fully how this Norton analysis works. Tomorow I’ll try the repairing (boot) version. This version of Norton is taken from the internet provider. It’s firewall is efficient so I wonder why these hackers can enter so easily, just by clicking on a webside marked with low risk (also, the risk of ramnit is level 2 low or something). Well, what should I do besides repairing the Windows instalation and fully resseting the pc?
PS: I decided to choose this category because, even if it was a hard choice between this and the toolbar (Symantec) one, I think this one is fits the most.