Hi Thomas123,
What you have to remember is that IE and FF (or FF-like browsers like Flock) each put their history, cookies and cache in other places. So if you have an alternate browser you have to treat cookie policy twice etc. Using an alternate browser is OK after you have upgraded and fully updates and secured IE. Also you must secure your alternate browser. Latest version always, also all latest upgrades and versions of add-ons installed. Use in-browser security. Run your alternate browser with Avast inside (see their instruction on their home-page), this is the same for FF and for instance Flock. Have add-ons like CookieCuller, NoScript, Adblock plus, and the preference bar to further tweak your security settings. In Flock you can use one governing password for all passwords used. Use NukeAnything, to take out any object you like of a web page, and install (15 k) the Dr.Web plug-in to scan all your hyperlinks for malicious code on their update server in St. Petersburg. Cookie files in FF are text file you can open it up in notepad, clean it out, and later FF will create automattically. In CookieCuller you can give certain cookies a protected status (also in Flock this works perfectly). There are other safety precautions: FraudEliminator add-on. I personally do not like searchbars or side-bars because of security and privacy implications, the preference bar excluded.
greets,
polonus