<windows root>\system32\hal.dll

Okay, I have the same problem. Now I have two PC's, one with XP pro as OS and with the error message.
The other with Vista Home OS which is the one I'm using for this quote.
Now on the Error one, I must Boot (and get the error) to open the CD Rom which I put my XP CD in and close. (CD Rom reads Disc and nothing happens).
I then press the off/on switch, the PC boots and the Error message comes up and the Install/Repair XP does not, its only black screen with the error message at the top, pressing, Esc. & Enter re- boots and the result is the same as above. This PC contains numorous Games and Files I must keep.
Please Advise.

Change the boot sequence in your BIOS so that it boots to the CD Rom drive first. Most computers you can get to the bios by holding down the delete key as soon as you turn the computer on, or in some cases, the F1 or F2 key.

Okay: 1: I got the BIOs 2: I shifted over to the BOOT tab. 3: I moved and high lighted the CD-Rom Line and pressed Enter. 4: A small Blue Menu appeared on screen with Selections a: Disabled b: my CD-Rom (which was High Lighted) c: my DVD-CD. 5: I pressed Enter. Menu closed. 6: Moved Tab to Exit, pressed save & Exit, answered "Yes" to confirmation.
7: Re-Booted, still no XP , just black screen and error message.

Did all this again for DVD-CD player, same results. ??? Both times the lights on both players showed Disc being read ??. Any Suggestions, Despert in Montreal. PS, I don't have a Floppy Back up for XP Pro just the CD for OS XP Pro.

Try method's 2,3 & 4 in that order in this link:
http://support.microsoft.com/kb/314477

take a look here i just replied to someone with the same problem

mswindows-forum/windows-root-system32-hal-dll-file-corrupt-missing-t95193.html

Okay, using methods 2,3 & 4 require that my XP Pro CD is acted on and the Install Menu comes up.
But as I've noted above it does not, even when I change the BIOS to boot on another player. Thats the problem I can't get my XP Pro CD to open. ????

When you see the screen that offers you the option to enter "Setup", I.E. the BIOS, there should be another option to enter the Boot menu. Might be F2, or possibly F12

That should let you choose CD

to get in to your bios it is del on the boot screen or F2.. with newer computers you can get to a 1 time boot menu by hitting F12
also remember to save the setting before exiting the bios.