Deleting history

My computer has had so many viruses because of the internet. How do I delete my computer's Internet history without deleting my computer's history?

In internet explorer, it's tools, internet options, content, then select delete browsing history or similar.

In firefox, it's under preferences, privacy, private data, then select clear private data.

Also, generally speaking, firefox is safer than IE as most viruses are spread with Active X controls, etc, which are only available in IE aren't in Firefox. Firefox is also free + faster.