I switched from Firefox to Chrome about a year ago because FF seemed to be getting slower and slower for me. Chrome will import all your FF bookmarks easily, so don't sweat that at all. You can keep FF installed and download/install Chrome to give it a try.
I'm on Windows 7 64-bit OS. For anti-virus/malware protection I use Vipre and highly recommend it. It's got a much smaller "footprint" and is much less intrusive than Norton. Very highly rated in independent tests as well. It's not free but very, very good.
Emily
2011 Jamis Dakar XC "Toto" - Selle Italia Ldy Gel Flow
2007 Trek Pilot 5.0 WSD "Gloria" - Selle Italia Diva Gel Flow
2004 Bike Friday Petite Pocket Crusoe - Selle Italia Diva Gel Flow