Hosed my system - anyway to ask yum to fix it?

Folks

I seem to have hosed my system some how.  I posted here:
https://www.redhat.com/archives/fedora-list/2009-July/msg03500.html
And the verdict seems to be dead disk, but it's not, or may be it is...

I've lost some files from the system and I'm able to log in to
runlevel 3, but X/gdm seem brocken (no doubt amongst others) so no
level 5.

I've run
rpm -V -a
and gone through the list with
yum reinstall
for each package indicated, and hoped that would fix X/gdm, but it
didn't (though I start up now without failures, except for cups)

So, I've run
yum reinstall @"X Window System" @"GNOME Desktop Environment"
but that hangs after the first package erase/install (metacity) with
(following ^C)
Error in POSTIN scriptlet in rpm package metacity...
error: %post(metacity...) scriptlet failed, signal 2
(... = version etc)

Googling on that led me to:
http://www.mail-archive.com/[email protected]/msg04654.html
So, I attempted to turn off prelinking (floundering round in the dark)
but running
/etc/cron.daily/prelink
seems to hang itself - whether turning it on or off in
/etc/sysconfig/prelink

I suspect I've got myself in a bit of a pickle...

Is there any magic yum command that'll check for missing files for all
installed rpms and put them back in?

Is there any magic anything command that'll tell me definitively if I
should chuck the hard drive, which I really don't want to do because
although I've got backups, my backs against the wall at the moment and
I really can't afford to be doing this......

Life, thanks
Morgan.