Thanks for all the help and suggestions Chris 
1. do you mean QT actually launches as Windows launches? With a QT window opening and displaying all the annoying latest available online content?
No but the process starts running in the background. By default I think it installs itself in the system tray (bottom right) but even if you get rid of that the qttask.exe runs at startup. Thanks to Dan Schwartz for the registry tweak to stop that. Shouldn't really require a registry tweak though should it! And one has to remember where this registry tweak is or go hunting for it after a Quicktime update.
Is this enabled / disabled in "preferences"?
No
2. Can't you customise the quick launch bar?
Yes, it's a very minor issue.
3. should be able to disable this in "preferences".
I think so although this Apple update thing keeps coming back to life. Probably because I have iTunes too.
4. This sounds like a bug that Microsoft have inside the OS? or is it just a compatibility thing
It's a compatibility thing but basically it's Apple just not supporting browsers on XP x64. And I'm talking about the 32-bit browsers, not 64-bit IE7. There are a significant number of us using this OS, but I suppose not enough for Apple to bother fixing it.
have you ever tried to go back a few versions? All the way back to the first H.264 version number 7..... ?
Not yet. I might hunt around for a download and try that.
blimey - does this mean you can't watch my Ocean Rover vid then, Nick?
Your Ocean Rover video is not embedded but a direct link. If I left click it opens a new tab and hangs with the right click "pro"options doing nothing. I can however do a right click on the original link and chose "save as", same as I can for Shawnh's videos (By the way I saw your Ocean Rover promo ages ago when i was running 32-bit XP. Nice job!)
Right-click and save target as (or other option) and download the linked file......
This is how your
Minhasa intro page looks on IE7 or Firefox 2.0.0.9:

Followed by this (IE7):

or this (Firefox):

Followed by the browser crashing.
Followed by much cursing because I've lost all those tabs I had open 
Personally speaking, the sooner Quicktime goes the same way as Real Video, the better.
Use Flash video for embedding! Everyone can play Flash and the quality is great these days with the On2 VP6 codec 