Can't play Doom Trilogy. Help!

If anyone can help me retrieve or find Dplay.dll that will work and agree with Win 7 64-bit OS.  
I can install 'Collector's Edition Doom: The Ultimate Doom Trilogy' but it won't load. It gives me an error message that states:
"Dplay.dll cannot be found on your computer..."...so it's a Win 95 thing, but this one was built for Windows XP
I have tried all DX updates but then found that folks are having trouble with Vista-64 OS's installing (and mine is the Vista Home Build 7600 kindly referred to as Windows 7).
No amount of compatibility mode help did anything at all, and some of these .dll download sites are full of crap and don't look very trustworthy.
Thanks for any help you can provide.