I think there are some guys on Channel9 forums who know much more about IT security than me, so I would like to ask a few questions here.

I have a Windows XP Home Edition computer with SP2. The Windows firewall is active and I even set it to block exceptions. I have installed a NOD32 antivirus software and Spyware Doctor from Google Pack. I run full scans with them regualry, plus sometimes I scan the system with Nessus and Microsoft Security Baseline Analyzer.
As you can see, my system is quite well covered... BUT:
I use IE7 and OutLook Express and (according to Secunia) they both have unpatched security holes.
My question is: is it safe to use them? Or using them makes all my security precaution useless and my system can be corrupted by some malicious code?