For all those that have had MTP problems with XP SP3 and Samsung Tabs
I must have wasted a day or two on and off idly trawling the Internet looking for solutions:
Windows XP SP3, Samsung Galaxy Tab 8.9 with 3.2, latest Kies, and latest everything else.
This thread led me to a solution but all I did was reinstall Windows Media, connect the Tab again and, boomph, it worked first time. No deleting drivers, nothing, and what's more the Windows Media version I had was the current version which I reinstalled over anyway.
Hope this shows up prominently in Google searches so others don't waste as much time as I did.