I have both the DirectX files as downloaded from FalconFly.de in January 2012. The .zip files are NOT corrupt, but I have not tested the .exe files inside.
I have the Quantum3D file as downloaded from FalconFly.de in Feb. 2005 (not corrupt).
I think you can get the SFFT driver from 3dfxzone.it via the Wayback Machine, although the file name is slightly different:
https://web.archive.org/web/20060607174514/http://www.3dfxzone.it/public/files/S...I don't have the mesafx file in .zip format, but I do have MesaFX-6.1.0.9.exe, so you could probably execute that and ZIP the decompressed contents (as I recall you did that sometimes in the past).
I will PM my email address.
(Edit) File sizes are as follows:
DirectX-90c-x86-x86_64-Feb2006.zip (51338769 bytes)
DirectX-90c-x86-x86_64-Jun2006.zip (54814471 bytes)
manual-Quantum3D-HeavyMetal.zip (2429159 bytes)
MesaFX-6.1.0.9.exe (1777673 bytes)