I want to play games that previously ran on win7. However, I have win8.1 now and I purchased Doom3 and windows 8.1 will not recognise the program; not even an .exe file.
Has anyone solved this issue?

I probably wont be much help, but I assume you have downloaded the game via Steam. If so, try launching the game through the Steam launcher.

If you installed it off of a disk then try compatability settings back to Win 7 or XP. Then try with admin access. I know Windows 8 can be a real pain in the ass.

I have not had any problems so far with win 8.1

check out

http://www.microsoft.com/en-us/windows/compatibility/CompatCenter/ProductDetailsViewer?Name=Doom%203&vendor=Activision&ModelOrVersion=1&Type=Software&tempOsid=Windows+8.1

several questions down is a question about doom3 from steam on win8.1

yeah above doesnt say much but I did find this :

Doom 3 BFG Edition works just fine on my Windows 8.1 PC. There was an issue with the OpenGL library shipped with some versions of the AMD Catalyst drivers which would cause the game to fail to load. I believe that this problem crept up around Catalyst 13.4 (prior versions were unaffected) and was resolved around 13.11. I'm running Catalyst 14.6 beta without issue.

also:
Thanks for the tip k.doyle.w. Running these two installs (as per the support page):

...\Steamapps\Common\DOOM 3 BFG Edition\directx\DXSETUP.exe
...\Steamapps\Common\DOOM 3 BFG Edition\msvc2010\vcredist_x86.exe

fixed it for me :-)

Thank you. I have an AMD processor, however, I am confused as to what Catalyst is? Is it the graphics card? It is an AMD Radeon HD 8550G...I am new to this. I recently purchased this computer and it came with win8.1. I will try to download the above. I purchased Doom3 BFG at a dept store. I will let you know.... Thanks again!
... OK... now I am really confused! I have the disk sitting in front of me... I checked out above file directories; Doom3 BFG is not even listed! I re-installed the darn thing and "Nothing!" ... Now what do I do? This is really frustrating! Thanks for your patience!

Catalyst is the graphics card driver.

The Catalyst Control Center or CCC is the AMD driver package for gamers running AMD based graphics cards and is also the application that lets you change what settings your graphics card is using. The latest versions are available at http://support.amd.com/en-us/download

Also if you have a physical copy of Doom 3 from a retail store, then you typically wouldn't have the steamapps directories, those would only be created if you had purchased Doom 3 through steam and had downloaded/installed it from there. When you did the installation of Doom 3 from the disk what install directory did you select? If you are unsure you can right click on the Doom 3 shortcut and choose the 'Open File Location' option that comes up in the context menu to see the games directory, then you can look for those directx and msvc2010 subdirectories to see if they are there,

this part is if you had purchased from steam. At the time of my posting I had no clue where you purchased it. Since you have the disc disregard this part.