steam + dvd want to install mod and patch

[cocoloco]

Hi
My aim was to play totalwar with the least bugs and use SS v4.0 or v4.1
I own the box with the metal man and cards but i couldnt find my dvds so i bought it via steam as it was so cheap.

the steam version appears to be v1.03 and I wasnt sure if this still contained the sheild bug and it seems i cant install the v1.2 patch needed for stainless steel v4.0

so I went to look for my orginal dvd to install which I have found in the shed and installed on pc witihout removing the steam version and it works as ive tested it no conflict seem to happen.
I then used the v1.2 patch to install over the dvd install which is v1.0 but i get an error with the infomation.

Incorrect patch version. cannot continue with the install process.

Can i have some help please.

I prefer not to redownload the steam version took some time.

is the steam v1.03 a good version? can SS v4.0 work with steam?