XP won't boot

I'm working on an HP Pavilion that I installed a new hard drive in about
two years ago. It's Home Edition SP3, up to date.

He shut it down normally one night. The next morning it wouldn't boot. It
is coming up to a blank black screen with a flashing cursor in the upper
left corner. The only key that will intercept it is F1 which brings up the
BIOS setup. The hard drive is listed there as primary master.

F8 will not bring up a menu. If it would have, I'd have gone for Last Know
Good Configuration.

Next I booted up a recent version of Hiren's and ran Mini Windows XP. It
reads the drive fine and I was able to copy all his documents, favorites,
mail and a couple of other folders to an external hard drive. So we've
saved his stuff.

Next I booted with an XP install CD and went in to the restore console. I
ran chkdsk /p. It came up with the usual screen and included the line
"Chkdsk found one or more errors". It doesn't really say whether it fixed
them or not, but a subsequent run of chkdsk didn't have that line. I also
ran "fixboot".

Still no joy. Just the black screen with the flashing cursor.

I went back to the Hiren's CD and ran two different hard disk diagnostic
tests, one of the was Western Digitals DLG, the other one was HTTD. Both of
those showed no errors.

I also slaved the drive to my shop computer and ran chkdsk on it from
Windows. It came up there clean as well.

It seems like I've had this before and have always seemed to diddle it out
of it one way or another but this time it's not happening.

There's a restore partition on the drive but that will put it back to
Service Pack 1 and it'll take forever to install service Pack 3 and 130+
updates that have come out since SP3. Plus copy all his stuff back,
reinstall other software, printer, etc.

Any suggestions as to how to revive this thing?