If you're having the TESV.exe - Bad image d3dx9_42.dll error like my girl friend was; the solution is found here
These may be located differently for Win 7 vis-a-vis Windows XP (which is what I thought you were running).
The files on Win7-64 are stated to reside in
I found a post on the Steam forums regarding a similar issue. Although the game is different (Skyrim) the problem seems the same as does the potential solution -
I'm not very familiar with Win 7 but one thing you may need to check is the location of the DirectX .dll files that need to be deleted.
After a lot of digging around on forums it appeared it was something to do with Directx and an application extension XINPUT1_3.dll. Anyway to cut a long story short I found this on the DC Universe Online support forums, http://forums.station.sony.com/dcuopc/posts/list.m?topic_id=5948 , and rysohl's post about halfway down worked for me (I didn't delete the file I moved it to a memory stick just in case) - anyway here it is, as follows
"Don't know if anyone is still having this issue, but for the record... I got this error after installing on my new system running Windows 7 64-bit. The issue is that even though it says the problem is in the C:\Windows\system32 directory, the file causing problems was C:\Windows\SysWOW64\xinput1_3.dll. I deleted this file and reinstalled DirectX, which replaced the file and it ran fine after that. Hope that helps anyone else who comes across this issue..."
I downloaded Skyrim The Elder Scrolls V from Steam yesterday and had a similar problem. When I clicked play nothing happened.
Link in case you want to read the thread -
I've seen dozens of people asking for help with this error across the net with no solution, and I'm just spreading the word, so if you'll excuse me, I have some more boards to post this on.
(Sorry about the formatting, this post if formatted for SPUF, not SPUD. SPUF forever!)