HAL.DLL and hard drive portability problems.

I have a two+ year old Dimension 4700 running XP Media Center and a one year old Dimension 3100 running XP Home. The 4700 had ben put into standby and when I tried to bring it back to life it was very slow. I found that the CPU useage was 99% running the standby startup program (don't remember the exact name). I have seen this type of issue on another computer with an earlier OS and a reboot cleared the problem so I did a regular turn off sequence. On reboot I got a message that the HAL.dll file could not be found or was corrupted. I know that service pack 2 provides for a backup of this file but my problem is accessing the files and replacing the corrupted/missing file with the backup. I have attempted to boot from CD and am unable to do it. The machine continues to attempt to boot from hard drive even though The bios only lists the CD drive as a bootable source. This issue has been discussed at length on this forum. Next alternative was to move the hard drive to anothe XP computer as a slave or second drive. Both of my Dell computers have SATA drives so I hooked the drive from the 4700 into the 3100 and configured the BIOS for two internal drives. The 3700 recognized the drive but would not read it. I only got a message that the drive was not formatted. But, the 4700 is reading it and trying to boot from it with only the HAL.dll error being reported. Where do I go from here? Larry