Here is a tip to uninstall Symantec Antivirus (I use the corporate edition) when the uninstall password has been forgotten (NOTE: the default password is symantec) OR you are using a Symantec Antivirus Server to manage clients and the server has been reinstalled or corrupted thus losing the server group root certificate (stored in the 'pki' folder located in C:\Program Files\Symantec AntiVirus, this should always be backed up!).
A while ago I had an old computer with a single IDE hard disk in it running Windows XP Pro with many applications installed. I had a second computer with totally different hardware (different motherboard, vga, lan etc) and I wanted to move the hard disk from the old computer into the second one, retaining my windows installation/applications and boot from it. I was determined not to install Windows XP Pro again so I started looking into why the disk wouldn't boot when moved onto new hardware. It turns out that it's a problem with the driver for the IDE controller.