you need IWAD - main wad file, like doom2.wad or doom.wad or plutonia.wad etc.. - depends on what server use and PWADs - additional wad or pk3 files, like for example dwango5.wad or duel32.pk3 - also depends on what server use usually IDE downloads and installs PWADs automatically if you dont have it, except commercial IWADs (doom2.wad, doom.wad, plutonia.wad, tnt.wad, heretic.wad, hexen.wad) - you have to buy and install them youself (not all - only what you need)
now i got another problem zdaemon thinks i got a pirated copy of doom2.wad even though i did not get it illigaly (PM me if i spelled it wrong) and does doom 2 or ultimate doom work on windows 7?