i installed ubuntu now i cant find my windows xp

in ubuntu open a terminal type sudo gedit /boot/grub/menu.lst

at the bottom add this:

title Microsoft Windows XP Home Edition
root (hd0,0)
savedefault
makeactive
chainloader +1

then save and reboot

how do open a terminal type sudo gedit /boot/grub/menu.lst

applications menu> accessories>terminal type sudo gedit /boot/grub/menu.lst then enter your password when it asks then add this at the end:

title Microsoft Windows XP Home Edition
root (hd0,0)
savedefault
makeactive
chainloader +1

i did what you said and got this error during boot up
Error 13: Invalid or unsupported exectable format

press any key to continue

what happens after you press a key

it take me back to the 4 choices to boot three are the ubuntu the other is windows xp

so what happen when you hit xp

it gives me the Error 13: Invalid or unsupported exectable format

press any key to continue

and it takes me back to the 4 choices

oh ok please type in terminal sudo /boot/grub/menu.lst and copy and paste the content to this page

oops meant sudo gedit /boot/grub/menu.lst

# alternative=true

## should update-grub lock alternative automagic boot options
## e.g. lockalternative=true
## lockalternative=false
# lockalternative=false

## additional options to use with the default boot option, but not with the
## alternatives
## e.g. defoptions=vga=791 resume=/dev/hda5
# defoptions=quiet splash

## should update-grub lock old automagic boot options
## e.g. lockold=false
## lockold=true
# lockold=false

## Xen hypervisor options to use with the default Xen boot option
# xenhopt=

## Xen Linux kernel options to use with the default Xen boot option
# xenkopt=console=tty0

## altoption boot targets option
## multiple altoptions lines are allowed
## e.g. altoptions=(extra menu suffix) extra boot options
## altoptions=(recovery) single
# altoptions=(recovery mode) single

## controls how many kernels should be put into the menu.lst
## only counts the first occurence of a kernel, not the
## alternative kernel options
## e.g. howmany=all
## howmany=7
# howmany=all

## should update-grub create memtest86 boot option
## e.g. memtest86=true
## memtest86=false
# memtest86=true

## should update-grub adjust the value of the default booted system
## can be true or false
# updatedefaultentry=false

## ## End Default Options ##

title Ubuntu, kernel 2.6.20-15-generic
root (hd0,0)
kernel /boot/vmlinuz-2.6.20-15-generic root=UUID=76f4f04c-4dbe-4e08-afdb-adf021104446 ro quiet splash
initrd /boot/initrd.img-2.6.20-15-generic
quiet
savedefault

title Ubuntu, kernel 2.6.20-15-generic (recovery mode)
root (hd0,0)
kernel /boot/vmlinuz-2.6.20-15-generic root=UUID=76f4f04c-4dbe-4e08-afdb-adf021104446 ro single
initrd /boot/initrd.img-2.6.20-15-generic

title Ubuntu, memtest86+
root (hd0,0)
kernel /boot/memtest86+.bin
quiet

### END DEBIAN AUTOMAGIC KERNELS LIST
title Microsoft Windows XP Home Edition
root (hd0,0)
savedefault
makeactive
chainloader +1

unless you have two hard drives it looks as if you deleted your windows partition but to make sure post the output of
sudo gedit /etc/fstab

# /etc/fstab: static file system information.
#
# <file system> <mount point> <type> <options> <dump> <pass>
proc /proc proc defaults 0 0
# /dev/sda1
UUID=76f4f04c-4dbe-4e08-afdb-adf021104446 / ext3 defaults,errors=remount-ro 0 1
# /dev/sda5
UUID=5d015b50-5883-43eb-bcac-507a419b1edb none swap sw 0 0
/dev/scd0 /media/cdrom0 udf,iso9660 user,noauto 0 0

show the output of
fdisk -l

P.S. that's an L not an i

i typed fdisk -l

and i get no command found

sorry I mean:

sudo fdisk -l

Disk /dev/sda: 320.0 GB, 320072933376 bytes
255 heads, 63 sectors/track, 38913 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot Start End Blocks Id System
/dev/sda1 * 1 38160 306520168+ 83 Linux
/dev/sda2 38161 38913 6048472+ 5 Extended
/dev/sda5 38161 38913 6048441 82 Linux swap / Solaris

Disk /dev/sdf: 250.0 GB, 250059350016 bytes
255 heads, 63 sectors/track, 30401 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot Start End Blocks Id System
/dev/sdf1 1 30401 244196001 c W95 FAT32 (LBA)
dhillon@dhillon-desktop:~$

ok I see the problem type sudo gedit /boot/grub/menu.lst

then erase what I put earlyer and put

title Microsoft Windows XP Home Edition
root (hd1,0)
savedefault
makeactive
chainloader +1

then save reboot and se if it worked

no luck its says starting up but it takes 10 minutes and no progress

i do have an external usb HDD its 250gb attached should i de attach it and turn it off

I have no Idea how to fix this but I would suggest going to www.ubuntuforums.com and submitting your problem there

First, maybe windows still has it's own bootloader on the second drive still, try changing boot order in the bios to boot from the second drive.

Another thing is that you may need to make this menu.lst entry a bit longer:
title Windows XP Professional
root (hd1,0)
savedefault
makeactive
chainloader +1
map (hd0) (hd1)
map (hd1) (hd0)

See also: https://help.ubuntu.com/community/How_to_dual-boot_Ubuntu_and_XP_after_installing_them_separately_on_two_HDs

If all fails try using some third party boot utility like:
- Super Grub Disk: http://supergrub.forjamari.linex.org/, or
- EasyBCD: http://neosmart.net/dl.php?id=1.