Right so I just bought an ultra cheap steam copy of Deus Ex, and initally couldn't get it working due to a stupid speed problem (main menu was super laggy and seized up). Luckily some nice guy provided a fix. See link below.
Get this: Download this archive , and extract to your system folder.
Thread: Forums.steampowered.com
Now that you have Dues Ex working you might want to play some mods. All you have to do to get mods working is replace your mod exe in [in your deus ex/system folder] (e.g. HDTP.exe) with a copy of the CustomDeusEx.exe [which you'v just installed] renamed to the name of your mod exe. See example.
Example [using HDTP]:
0)Install HDTP mod (duh lol).
1)Remove/Backup HDTP.exe.
2)Make a copy of "CustomDeusEx.exe" and rename it to HDTP.exe.
3)Launch HDTP.exe
Please Note the shortcut provided with the mod will NOT work. Consequently you will have to create a new one (shortcut of your new HDTP.exe). I think everyone reading this will know how to do that so no worries. :)
For a bonus I'd like to suggest a mod: DeusEx Ultra High Quality mod. This is simply a compination of HDTP (a texture pack) and the enb series for deus ex (preconfigured).
Helderpinto.com