Yes there will be no problem at all, and GTX 670 has drivers for WinXP http://www.nvidia.com/object/winxp-301.42-whql-driver.html
Yes you will, but be noted that some of the recent games are not supported anymore with WinXP, and WinXP has some limitations to hardware so you'd be better gaming on Win7.
BF 2142? :O
Wasn't that a game introduced in 2006 or later? :O
GTX 670 is able to play BF3 on 3 monitors @ high settings.