First of all, I'm dual booting XP and Ubuntu.
Basically, I download Ubuntu while I'm on XP, restart my computer, start it again and choose to start Ubuntu instead of XP, but I can still choose to turn of my computer and start on another one at any time.

But when I download Ubuntu and use it for awhile then quit and go to XP, I'll try to quit and go back to Ubuntu but when I select it there is a countdown from 10-0 in the system startup (you know, the menu that looks like Windows command line that you get on every system start up)If I press esc, it just takes me back, if I let it countdown, it takes me to a window in which it asks me to give a command, the list seems to be nothing of importance to me, already tried all of the obvious ones that could help me out.

Help would be greatly appreciated.

This sounds in vague terms like a boot prompt of some sort. In general, if you leave a boot prompt for 30 seconds or so then it will start booting; there's usually an option called linux (or possibly ubuntu) that will boot by default.

Perhaps you could post what the menu options are?

Another thing you can try: Can you boot from the original Ubuntu install CD and then choose the option "boot from first hard disk"? This may leave you back at the same menu, but I'd be curious to know if you still see the count-down.

There are about 40+ and I'm far to lazy to post all of them.
But its strange because it works first, or even if I restart, but if I actually turn of my computer and turn it back on, it just stops working.

You can also try posting this problem to the following forums:

justlinux.com

http://ubuntuforums.org/forumdisplay.php?f=326

If you are to lazy to post something about your problems then what are you doing here?

I hate to say this, because I respect the fact that you have come to us for help. But you really do come across as making it difficult to diagnose your problem. We have asked you for information and you have not told us it, and that makes it impossible for us to know what's wrong. For example, even one or two examples of these "commands" might let us know if you are looking at a BusyBox system running on an ramdisk, a GRUB bootloader or some sort of BIOS.

What I can say is that computers sometimes failing to start when they boot up, but working reliably once rebooted, can be caused by using a power supply rated at slightly too lower wattage for the machine. The power requirements peak when the devices are turned on, and if the PSU isn't up to supplying this peak power, things can take too long to start up, and the computer starts booting before key hardware is present.

Then again, it could also be caused by a bug in your computer's BIOS, a loose cable somewhere or a fundamental flaw in the bootloader, so it would be nice to narrow this down slightly.