Shogun 2 crashes...

[Condottiere]

First post since 2007, so not sure if this is the right sub-forum, but I've been having problems with crashes since installing this game, on a brand new PC, in May 2011. On my old computer with WinXP it was easy to find and modify MTW 1 through Properties on the taskbar icon,but no idea where to find such on Shogun 2 with Win7. Looking at the crash fix solutions on Total War.com, I keep seeing lists referred to as DxDiag, but no idea where to find it and the suggestions mention accessing files that I cannot find - much easier, IMO with MTW 1. Embarrassed to admit it, but the solutions, no idea if they apply, appear complicated for me.

Processor: i5-2500k CPU @ 3.30 GHz 3.60GHz
RAM: 4.00 GB (3.49 GB usable)
System: 32 bit
875 GB free of 931 GB.
NVIDIA GeForce 8600 GTS

Windows 7 Ultimate

Installed:
Shogun 2
Ikko Ikki Clan pack
Sengoku Jidai Unit pack
Hattori Clan pack
Blood pack
Rise of the Samurai

The game crashes before and on rare occasions, after battles, and since March/April, when skipping pre-battle speeches. Sometimes a crash would occur on the campaign map and almost always when accessing the clan management screen, after playing for a few turns. Have been playing on Legendary since first install, but spending more time re-starting Windows than "enjoying" the game.