The safest combination would be Firefox (see http://support.mozilla.com/kb/Installing+Firefox) plus two extensions
Noscript and Flashblock both of which you can download via their extensions option
these allow you control of when you enable javascript + flash - this gives much safer browsing (btw IE7 has regularly featured in several official 'do not use' lists but Microsoft have been adding security bells + whistles to it but Firfox is both much better and so far proved safer)
once you have these two installed then loading the Flash extension is ok as you are now in control