I still have a copy of the alpha release version of CounterStrike here somewhere. As I recall, probably as a self-extracting exe but maybe a zip file, and it was about 8 megabytes; that's not quite so amazing as it sounds, as it was purely a mod for Half-Life and sat on top of an existing Half-Life installation.
I should check that it's available in historical repositories and if not, see where I can send it for posterity.
Please do - all the betas have been archived but I don't think many (any?) of the alphas were conserved.
Much like Day of Defeat - only ones of the alphas seems to have survived to the present day.
I should check that it's available in historical repositories and if not, see where I can send it for posterity.