Install as follows: First delete other mods from the ETW data folder which is C:\Program Files (x86)\Steam\SteamApps\common\Empire Total War\data.. Then download here. Also download this crashfix here. NB in instructions below, "yourusername" means whatever your PCs username is.
1.Place user.empire_script in C:\Users\yourusername\AppData\Roaming\The Creative Assembly\Empire\scripts. Delete the previous scripts already located there first.
2. From the first download, Place 1600_naval_007.pack, Col_loc_en.pack, Col_music, Col_scripts, Col_models.pack, Col_ui.pack, colmod.pack, Colo_events.pack, Pikeman_animation_MOD.pack, and patch_general_andy's_musket_sounds.pack in C:\Program Files (x86)\Steam\SteamApps\common\Empire Total War\data.
3. From the patch.rar file, extract Colmod.pack over the original, in the Data folder. When asked do you want to replace the original of the same name, click Yes.
4.. Next place startpos.esf in C:\Program Files (x86)\Steam\SteamApps\common\Empire Total War\data\campaigns\main. Start ETW as normal.
The new startpos starts in 1607. I thought that was appropriate because that is when the first permanent English colonies were founded in the continental Americas.
If you have problems with the startpos you can default to the CA one by selecting "Verify Integrity of Game Cache" in Steam, but then the game will start in 1700 instead.
Additional French officer models and battle flags (based on Thirty Years War French flags). New units including Gardes Francaises Pikemen, early flintlock musketeers, French drummer model.
New Irish units including: Kern, Gallowglasses, O'More Pikemen, Light Pikemen. New Irish officer model. NB Ireland remains an emegent faction.
New Brandenburg-Prussian grenadier models. German factions have a new German swordsman unit.
New Maltese pikemen and drummer/officer,
New battle flags for England and France. New naval flag for Portugal.
Historical religion for Wurtemmberg and Saxony (Protestant). Saxony no longer Protectorate of Poland.
New ship models/textures courtesy of Bethencourt (forum member at twcenter.net)
Also there is a script which makes certain early units unavailable later in the period, and certain late units unavailable early in the period. Credits to terryman from twcenter.net/forums for that.