Thanx for the quick reply Xan, and it seems that I havn't really done anything too stupid judging by your questions
I have tried all those things however. When you right click on the altar it does give a use icon but nothing happens when you click it. When you right click the item, it just gives examine and drop icons, and when you left click on the Altar it says something along the lines of 'If you had the right tome, you could activate this Altar!' (don't remeber exactly as I'm at work and can't look)
So as you see I'm completely stuck :P
I find this remarkably odd however, as everything else in the game is so intuitive, and this 'should' be one of the easiest things to work out, but bizzarely its not??
Also in Helms hold are the armour guards in the entrance. Here you need to use the Etched Gem on the pedestal to activate them ( i know this because after failing a million times I had to start looking at walkthroughs - which incidentally state that you 'use' the gem and 'use' the grimoire on the respective items, but dosn't say 'how'

)
Did anyone else have this initial problem? I'ts hard to believe its just me lol...
Thx in advance,
Kutter