Hal.dll error preventing 2nd OS from starting

I have a PC I built about 2 years ago, with 5 hdd's, running XP home.
I recently added a 2nd XP Pro OS, on another of the 5 hdd's, so as to
dual boot. All went well with the new OS, until I added a 6th hdd. Now
when I try to get into the new OS, I am told the file hal.dll is
missing or corrupt. From the original OS, I tried replacing the
effective hal.dll using the install disk & the command "Expand
hal.dl_". It replaced the file, but still NOGO. I also checked the
boot order in bios, thinking perhaps the hdd this 2nd OS was installed
on might have gotten bumped off the boot order by the new hdd, but
that doesn't seem to be the case; it seems to be number 2, secondary
master. I'm stumped, anyone got any ideas?

TIA

Dan