Can not play flight simulator says d3drm.dll is not in vista

Is your game old? d3drm.dll is related to Direct 3D retained mode which is part of Microsoft's DirectX API, Direct 3D is very old (1997) and has been removed from Window's Vista, therefor creating the incompatability.

d3drm.dll as I have come to understand, was implemented in Windows XP, if you have a copy or know someone who uses XP you could try looking through :windowssystem32 folder for the d3drm.dll file and copying it to your own system32 directory.
If you don't have access to XP at all you could also try this link
http://www.dlldump.com/download-dll-files_new.php/dllfiles/D/d3drm.dll/5.1.2600.0/download.html
You may wish to take precautions before downloading as downloads from an unknown site can always be risky.

If you have a copy of Windows XP, but you don't feel like messing with Vista's system directory or copying it didn't work, you could always try virtualization. Running a virtual copy of Windows XP along side Vista would allow you to run older games while running Vista.

Virtual Box is free and in my opion, easy to use virtualization software, you could try that or you could try vmware but that costs money.
http://www.virtualbox.org/wiki/Downloads