Please see the image below to re-enable your optical drives in Windows (XP),
after running SF Nightmare.
It seems to be a bit buggy right now, and although i have had great success running ISO , MDS images of SF games with it, It does tend to sometimes crash my PC.
Here's a guide as to how to get your drive(s) back...
Click Start (on the desktop) and select the control panel,
Double click System (you may have to scroll down to the bottom of the Cntl panel window) and select Hardware <Tab> and Device Manager <Tab>,
Expand (click on the + symbol) next to the DVD/CD Rom Drives and if any have little red crosses next to them (Disabled), Right click to bring up a sub menu and highlight and left click "Enable".
Should bring back your devices within windows....
Hope this helps u out!!!