see http://ubuntuforums.org/showthread.php?t=187413

wget -q http://soultrap.net/andrejkw/install_qemu.sh
chmod +x ./install_qemu.sh
sudo ./install_qemu.sh

change the directory that in which you would like to place your hard disk image
cd /whereever
then
qemu-img create -f qcow 4oldwin.img 4300M

this creates a disk image to install windows onto, I've left it at 4.3 gigs so I can back it up to a DVD. Remove the "-f qcow" if you have troubles...
no while still in your disk images directory:
qemu -localtime -hda guest.img -cdrom /dev/cdrom -boot d -m 512M -win2k-hack

I had to remove the "-kernel-kqemu" (mentioned in articles I've linked to here) line or I would get BSOD.

if you experience problems with mouse pointer hanging in bottom right corner, like I did, try this before you start up qemu (WORKS!!!)

export SDL_VIDEO_X11_DGAMOUSE=0

My PC does not have any virtulization capablities so thats it for me, but if you have a newer-than-2006 PC, try this
qemu -localtime -hda guest.img -cdrom /dev/cdrom -boot d -kernel-kqemu -m 512M -win2k-hack

If you are using Ubuntu 7 or better and have a newer PC, try the instructions here https://help.ubuntu.com/community/WindowsXPUnderQemuHowTo

Or even try this alternative method found at http://tech.tolero.org/blog/en/linux/qemu-9-and-kqemu-for-ubuntu-dapper-...

add the following lines to sources.list

deb http://ubuntu.tolero.org/ dapper main
deb-src http://ubuntu.tolero.org/ dapper main

gksudo gedit /etc/apt/sources.list

1. sudo aptitude update
2. sudo aptitude install kqemu-common kqemu-source
3. sudo aptitude install module-assistant
4. sudo module-assistant prepare
5. sudo module-assistant build kqemu
6. sudo module-assistant install kqemu
7. sudo aptitude install qemu

and to run, all on one line in terminal,
qemu -localtime -hda guest.img -cdrom /dev/cdrom -boot d -kernel-kqemu -m 512M -win2k-hack

now to solve the no kqemu error, a little trouble shooting

sudo /etc/init.d/qemu stop
sudo /etc/init.d/qemu start

I can't verify this works since I cannot get kqemu to work on my computer (no VT), good luck!!