We still recommend Pentium III processors due to the stability and the fact that they have been tried and tested. In many cases, they actually perform better than a Pentium 4. Pentium III processors are now available in up to 1.2 ghz, so they are fast enough for a good number of plugins and as many audio tracks as your hard disk can handle. The motherboard's chipset is very important too. We recommend the Intel 815 chipset (E or B or EB) These all support at least 5 PCI slots, Ultra ATA-100, 512mb of memory (max) but do not support dual processors. We recommend 256mb of PC-133 ram. For operating systems, we recommend Windows 98 Second Edition, Windows Millenium Edition (ME), or Windows XP (but check compatability with all of your hardware and software, especially your pro-audio hardware before deciding).