am trying to boot from 1gb usb stick, this fails and windows open
 

am installing ubuntu from 1gb USB stick. However, this fails even after i have hit the del, f1, f10 key. Instead windows xp opens up. what can i do

When you initially boot the computer, it should indicate which key to press (repeatedly) to enter setup. Computer manufacturers use different keys such as the ones you indicated. You will have to tell us who the manufacturer is or just watch the screen as a message should appear indicating which key.

When you access the BIOS, you should have a Boot heading where you may be able to set the usb to first boot priority.

In addition by what method did you create the bootable USB drive?

To clarify a bit, there are three things that can go wrong
1. You pressed the wrong key. It should display what key to press at the beginning.
2. You pressed the right key, but not fast enough. Most BIOSes only give you a couple of seconds before they start loading from the default disk. If you have to read the on-screen instructions, by the time you've done it you generally have to press reset to get them back again.
3. The USB stick has a bad (or even no) bootloader, so BIOS can't use it.

How old is the computer? Because the computer has Xp on it, there is the possibility that the computer doesn't have the ability to boot from usb, or only usb's formated in one way.

[OT] Hmm, looks like I have to make a meaningless post to enable me to watch this thread. Sorry.

There are two bootloaders that you might try also.
On older machines or machines with "quirky" bios, booting from the cd-rom drive works where other methods fail.
You might look into downloading plop or riplinux.

Plop:
http://www.plop.at/en/bootmanager/download.html

Rip Linux:
http://sourceforge.net/projects/riplinuxmeta4s/

Either one may be your solution when the computer's bios are at fault.
Both can be burned to cds and used in your cd-rom drive when you start your computer.
Once they auto-run you can select drive to boot from or usb to boot or partition to boot on a given drive. (plus more in the case of rip linux)
Grub4Dos is part of Rip Linux and it works very well indeed.

Another thing worth mentioning, making sure that the drive you use has a valid, undamaged 'Dos label' and that the drive has it's "boot flag" active and has a valid, error-free file system structure on it.
Hope that info is helpful.

A few tips:
The BIOS may identify the usb stick as one of the hard drives.
If you are still having trouble try the usb stick in another computer to see if it works.
You can always burn a an Ubuntu CD and try that.