linuxthreads to NPTL 2.6 kernel

[TripleE]

Yes, I have done it. I have somehow screwed up my Zimbra server (personal server). It will not start. When i tried to reinstall/upgrade Zimbra it failed at "NPTL...MISSING". Now I am blaming the Xen install that I did on the same server, but I cannot confirm that even though it was the last thing I installed before Zimbra stopped working. After some looking around, I was recommended to check:
$ getconf GNU_LIBPTHREAD_VERSION
linuxthreads-0.10

$ uname -r
2.6.15-28-686

Now a 2.6 kernel should be showing NPTL not linuxthreads. NPTL is required for zimbra to run. So after some tinkering around. I uninstalled all the packages that I installed for Xen:
sudo aptitude remove binutils bridge-utils debootstrap python-crypto python-pam Python-pyopenssl python-serial python-soappy python-twisted python-twisted-conch python-twisted-core python-twisted-lore python-twisted-mail python-twisted-names python-twisted-news python-twisted-runner python-twisted-web python-twisted-words python-zopeinterface python2.4-crypto python2.4-pam python2.4-pyopenssl python2.4-soappy python2.4-twisted python2.4-twisted-bin python2.4-twisted-conch python2.4-twisted-core python2.4-twisted-lore python2.4-twisted-mail python2.4-twisted-names python2.4-twisted-news python2.4-twisted-runner python2.4-twisted-web python2.4-twisted-words python2.4-xml python2.4-zopeinterface

Then I uninstalled/removed Xen as root:
sudo -s
[ -d /etc/xen ] && mv -f /etc/xen /etc/xen.old-`date +%s` || true
rm -rf /etc/init.d/xend*
rm -rf /etc/hotplug/xen-backend.agent
rm -f /etc/udev/rules.d/xen-backend.rules
rm -f /etc/udev/xen-backend.rules
rm -f /etc/sysconfig/xendomains
rm -rf /var/run/xen* /var/lib/xen*
rm -rf /boot/*xen*
rm -rf /lib/modules/*xen*
rm -rf /usr/bin/xen* /usr/bin/lomount
rm -rf /usr/bin/cpuperf-perfcntr $(D)/usr/bin/cpuperf-xen
rm -rf /usr/bin/xc_shadow
rm -rf /usr/bin/pygrub
rm -rf /usr/bin/setsize /usr/bin/tbctl
rm -rf /usr/bin/xsls
rm -rf /usr/include/xenctrl.h /usr/include/xenguest.h
rm -rf /usr/include/xs_lib.h /usr/include/xs.h
rm -rf /usr/include/xen
rm -rf /usr/$(LIBDIR)/libxenctrl* /usr/$(LIBDIR)/libxenguest*
rm -rf /usr/$(LIBDIR)/libxenstore*
rm -rf /usr/$(LIBDIR)/python/xen /usr/$(LIBDIR)/python/grub
rm -rf /usr/$(LIBDIR)/xen/
rm -rf /usr/lib/xen/
rm -rf /usr/local/sbin/setmask /usr/local/sbin/xen*
rm -rf /usr/sbin/xen* /usr/sbin/netfix /usr/sbin/xm
rm -rf /usr/share/doc/xen
rm -rf /usr/share/xen
rm -rf /usr/share/man/man1/xen*
rm -rf /usr/share/man/man8/xen*

Next is getting back to NPTL:
sudo aptitude reinstall libc6

Now after a reboot, this worked for me. So I thought I would share it with you. I am not an expert. So please feel free to correct me.