NapoleonTW + Shogun2TW installation

How do I install Shogun2 without upsetting NapoleonTW, which I already have installed, and heavily modded?
Any help will be most appreciated. Thanks.

The two games are in no relation to each other. You can simply install S2 in any other folder and play it, it should not affect NTW in any way.

Thanks for the reply Voigtkampf.
Yes, I realise they will install as seperate games. What I'm getting at, is that STEAM will play a part in the installation, and I'm afraid that it will modify my (modded) version of NapoleonTW while it's installing Shogun2TW, thereby ruining my Napoleon game.
Should I rename the Napoleon game folder before Shogun is installed, or copy it to somewhere else, then paste it back after the Shogun installation is finished?

Outside of automatically patching, Steam will only try to alter your NTW installation if you tell it to via tools like "verify local cache".

If you normally use steam in 'offline mode' and thus have not kept NTW up to date with patches, it may try to automatically patch NTW when you connect it to the internet. You can disable that by right clicking on the game in your steam library, choosing properties, and then one of the tabs has an option for "update this game automatically". Set it to "do not update this game automatically" and you should be safe. NB: do this before you put steam in online mode! Once it's aware that a game has a patch it decides that you must have it before you are allowed to play again. NTW did not have many patches and it's been ages since the last one, months and months. Mods usually require the most up to date version of the game anyway.

Thanks Frogbeastegg for the advice.
But I've just been into STEAM, (still off line) with the intent of turning off auto updates for Napoleon. But on the Napoleon Properties/Updates tab, "Always keep this game up to date" is the only option. Trying to select the little arrow at the end of this line does nothing. No other options emerge?
In the Total War Centre Shogun2 forum I asked this question and Old_dude suggested that you need to actually be online before this option becomes available!
And as you suggest, I daren't go on-line for fear of Steam wanting to patch my game. I can't risk not being able to play my game, (I am in the middle of a long campaign that I started early this year), and having all the messing about of having to apply fresh mods again that match the latest patch, and starting a new campaign.
It's at times like this, even more than usual, that I hate STEAM!

Hmm, tricky. You could check the mod's forum to see which version of NTW it requires. If the mod states that it requires the latest NTW patch then you should already be up to date and therefore safe. Unless, that is, you are using an old version of the mod. Hopefully you can remember which version of the mod you used.

Or you could take a minor gamble. It doesn't look like NTW has been patched since summer 2010 so if you have been online with steam any time since then your game should be fully up to date and therefore safe. If steam knows about an update it will force you to have it no matter what you tell it, so the fact you are currently able to play the game without it demanding to update suggests to me that it is up to date. That, or you have been in offline mode for a year!