Testing

Firefox use Linux (Ubuntu is my fav distro).
IE6 use IE4Linux for Linux (Not the beta, but you could though ain't used it yet myself)
IE7 use XP in VMWare Server for Linux

VMWare Server (get version 1, as version2 is a kind disapointing)
I am a lover of virtual machines for testing, just recently had a hefty time installing VMware Server on Ubuntu 8.04, then I discovered this.

Update Patches
When downloading the latest update, keep the defaults, but recompile when it asks for the gcc compiler. You should not need to re-enter the serials, be sure to run the following when updating

sudo cp /lib/libgcc_s.so.1 /usr/lib/vmware/lib/libgcc_s.so.1
sudo cp /usr/lib/libpng12.so.0 /usr/lib/vmware/lib/libpng12.so.0

Another note to remember:
Use Legacy Driver for CD drive, cuz my drive is too new. Even if u have 64bit dual core, don't get greedy with processors, one processor should be enough :P

service pack3 for xp, need more than 3gig+71mb size for partition, better make it 5gigs if you want it to live more (Especially to install updates like ie7) :P