If you are web developer who prefers to use linux, but must (for the most unfortunate of reasons) test with IE6, then virtualbox has probably become your friend.

There is a known, very lightweight image you can find around the interwebs called TinyXP which is a virtualbox image of windows XP. It has been fine tuned (from what I can tell) to be very lightweight and fast, and even has some nice right click shortcuts (for instance when right clicking on My Computer you get extra options I've never seen before).

The only problem I had with TinyXP is that the driver that came with it was not compatible with the network card used by Virtualbox 3.1.
I have another Windows XP virtualbox image which works just fine using the PCnet-FAST III (Am79C973) Adapter chosen in the Virtualbox Network settings for my virtual machine image, as shown below:

While on my other XP image this network setup works fine, on the new TinyXP image I was getting a driver problem in the windows Device Manager as shown below:

To fix this problem you'll need to switch to another driver. The driver should already be on your system so don't worry, you won't need to download anything.

To do this you will need to right click on the network adapter shown in the previous screen and choose "Update Driver..."

From there you will be asked if you want to check windows update for the driver, Choose "No, not this time"

From there you'll be prompted to install automatically or from a specific location, choose to install from a list or specific location:

When asked on the next page whether to search or Don't Search, choose:
Don't Search. I will choose the driver to install.

Not quite, done. One more step:
you'll now be asked to select a nework adapter (Make sure "Show Compatible devices" is checked).
Choose "AMD PCNET Family PCI Ethernet Adapter" and click next

Your NIC should now be functioning correctly and the device manager should look like the following: