Hi Mallik
There was no upgade for SP6 (or SP5, just fixpacks) in the Support Packages and Patches section however in the Installations and Upgrades there looks like an SP6 (and SP5) installer.
Plus the SP5 installation guide (can't find the SP6 one) states that you should un-install previous Service Packs (I'm on SP3) and then install the new one.
