Can I use a Intel HD57DD motherboard with a Intel core i5-650 processor and use the on board DVI output with a DVI->VGA converter to connect to my monitor, so I can setup windows, or will I need a separate graphics card?
Yes you can. The i5-650's video is integrated into the CPU package and will work fine with the H57 motherboards (which do not have a separate IGP on the motherboard.
i5-650 class CPU on the right in this pic.
crucial 4GB DDR3 1066 (PC3 8500), Seagate Barracuda Hard drives 320GB and a 1TB, both at 7200rpm, AverMedia TVHD Duet tuners and nMediaPC 5000b with 2x20 lcd display, as well as a nMediaPc 2.4Ghz keyboard and remote.