Windows XP help...?

I have computer with Windows XP Professional. Though there is a problem with a file and i can't fix it because i don't have the install disk. The computer is missing the hal.dll. files and I've tried downloading the files and i borrowed a friends install disk but it hasn't solved the problem.

the computer starts and acts like it is going to load all the way like it is supposed to but then it stops because its missing a file.

I've tried all the different methods of starting the computer but yet i have no luck.

Now i want to just put the Windows XP Home edition onto the computer but it wont load the program. it tells me to run a manufacturer-supported diagnostic or setup program. the problem is, is that i don't know how to do that and the computer won't start all the way.

How do i uninstall Windows XP Pro from the computer so i can put the Home version on.

Thank you i really need to get this computer running again and any help will be greatly appreciated.

Thanks for the time
My computer doesn't make it to the main screen were i can see the icons and the start menu so that won't work. thanks though.
Voxa8 I tried what you told me but it didn't pop up with the press any button to continue thing. any other suggestions?

thanks for your help though.

voxa8 is right.. however make sure that same key hasnt been used already or chances are you'll only get a trial version of xp installed.

you need to enter bios, turn off and back on again and start tapping DEL immediately until bios appears look for boot sequence, you need cd-rom firsthard drive second and floppy third, then save changes and exit, insert the xp disc and turn off, then start pc and it will say press any key to boot from disc, hit the space bar or any other key and it will boot from the cd, then click to install a fresh copy of xp and make sure to format the c partition once that is done continue with installing xp, after that is finished you need to install the drivers, this enables the sound, ethernet port etc

go to start in the left hand corner os the page. click on my computer. then on add/remove programs