As I'm writing this, I'm in the process of installing Windows XP on the Eee PC. I ordered a brand new copy of XP SP2 from the Microsoft Company Store for the purpose. Interestingly, there is an option in the Eee PC BIOS for installing the OS. Here's what you have to do to get started:

1. Hook up the USB CD or DVD drive (in my case, a Sony DVD-RW) to the Eee PC.

2. Boot up and press F2 during startup to get to the BIOS.

3. Go to the Advanced tab, enable all the devices and change the OS INSTALLATION item to Start.

4. Save the changes and reboot, pressing ESC during startup to get to the boot device menu, then select the USB drive to boot from.

The familiar XP Setup screen appears. I deleted the partition on which the Linux OS was installed, created a new partition from the free space, and selected it to install XP to, with a quick NTFS format. Erring on the side of caution, I didn't delete the small (8 MB) system partition.

The  XP Setup screen on the Eee PC

Copying the Setup files took several minutes (as always). After the file copy and first restart, I got the message that "NTLR is missing." I figured that meant I should have deleted that small system partition, so I ran the Setup program again and did so.

That was indeed the key; this time Setup proceeded to the GUI phase.

 
The graphical portion of Setup starts

This part of the installation wasn't particularly fast, but it wasn't a lot slower than on some other computers to which I've installed XP, either. All in all, it took approximately 40 minutes.

 
It's starting to look a lot like Windows

Of course, the first thing one is compelled to do after installing XP is to switch to the classic theme and change that awful wallpaper. :)

 
Now it's looking better than (default) XP

I still have a bit to do: installing Outlook and Word (just those two, to save space), optimizing the paging file, compressing the drive and performing all the other recommendations in the Asus manual to enhance performance. So far, with just the OS, it's running acceptably fast (okay, I admit it: faster than Vista on the Sony with Aero turned on).

So now I have a tiny little XP PC. Cool!