What I know is that the E.E. version (v1.4) is censored. You can tell by the cards of the girls. If theirs "boobs" are covered, then you have the censored version. If they're showing the entire boobs, including the nipples, then you have the E.E-D.C. version (v1.5). Also, the "readme.rtf" file in the game's folder should say in the beginning version "1.5" instead of other text.

There's a patch to apply that upgrades the version from v1.4 to v1.5, found in the game's website. I don't know how it works in Steam, because I have only the GOG D.C. version 1.5 (uncensored).

I know there's more in the latest patch, but the main reason of the patch is to un-censoring things in the game, add more and to fix a few things.

This is what I found about v1.5:

What's new in The Witcher Patch 1.5:
Modifications:
· copy securities (DRM) are removed
· playing the game no longer requires the game disc in the drive
· patch solves problems with EAX and blurred graphics

Additionally:
· 5 bonus adventures made by the Witcher community: ‘Deceits’, ‘Blight of the Bogs’, ‘Wraiths of Quiet Hamlet’, ‘The Wedding’, ‘Merry Witchmas’.

Steam also has the The Witcher Enhanced Edition Director's Cut. I don't use Steam, but if they're like GOG then you should be able to just upgrade to the latest version, provided you even need to.

The Director's cut added in nudity and wounds/blood to editions that did not formerly have it. Just check and see if blood is spraying out of wounds when you fight people.

For the record, the Director's Cut came out after 1.5.
Patch 1.5 added those things Azrael360 mentioned but North American games were still censored and you had to manually uncensor it with unofficial patches until Director's Cut came out.

Thank you for the information. :)