2nd CD isnt installing/not recognised

[Davidrowntree]

can anyone help me, i downloaded Doom3 about a week ago and it took 3 CD's - first one installed fine then it sed something like please insert second disk so i did and then i pressed ok (the only other option was cancel) and the message just repeated as if i hadnt put a disc in. I thought it was just a dodgy download so i deleted it.

No i have downloaded Manhunt and it is the same problem the second disc isnt recognised, i have tried both my disc drives and a lot of other things. (the second disc is a .cab file about 600mb - its one file and its showing as a winzip file)

I thought maybe there was a reason why this is happenening
Any help would be appreciated...Thanks
David