If you're REALLY paranoid about security, just run Linux/Firefox like I do, and install the official Java2, which is loads better than the MS Virtual Machine. Solid as a rock. Don't be too quick to rat on Windows for Blue Screens. My dad just downloaded the latest nVidia Detonator drivers, and it was crash city! The older drivers are much better. My ATI drivers are awesome.
Outlook Express hasn't given me any virus trouble, so long as you have ActiveX and VB scripting turned off in IE6. I don't like that IE and OE have unified security, but I rarely use IE for browsing, anymore. Just watch out for 3rd party virus scanners. Some of them do some nasty hacks to get into your mailbox, and Norton destroyed my Inbox once (multiple accounts of this happening from different people). I eventually disabled e-mail scanning, and all seems fine.
My only gripe is the machine boots up in 20 seconds flat, but takes 1-4 minutes to shut down. Yay for NT! :-)