My dedicated recording rig is not dual boot, but uses two hardrives, one for windows and music siftware, the other for music to be stored.
About attaching things to your PC, the solutions are often as costly or more so than your PC was. MOTU makes a unit callet the 896, great entry level interface. There is also the Tascam FW-1884, I use one, sold a 24 chnnel Mackie board, a Mackie control with two expanders, a Motu HD192 and a Motu 2408 MK 3, a Presonus M80, a Presonus ACP88 and a few misc items and replaced the ALL with just a Tascam FW-1884. It is an amazing little unit. Yes, it will do 5.1 surround.