here's what you need to do.
Find the path to the file and write it down. It will be C:/blah blah blah
Boot into the recovery console and log in as admin. CD to the directory the .dll is in and type:
del hal.dll
you might have to do:
del /F hal.dll
Once the file has been deleted, restart windows. The kernel will see that the file no longer exists and prompt you to insert the windows XP disk to correct the problem. It will install the file and all will be good. You can also try to repair windows, but it's not guarenteed to be sucessfull like deleting the file and rebooting is.