Wingroove had a mode where it would install itself as a driver that could be chosen for MIDI. Only thing is, last time I tried it, on a Windows 2000 box, it didn't work. But it did work on good old Windows 98. So your mileage may vary. There's another interesting roundabout way that'll let you use any SoundFont you might have, which allows for more possibilities and also works on the newest Windows versions, but the link I kept in my bookmarks doesn't work any more. If I can find it again I'll link it.
Um, I think you just go into the settings on the program, check Driver Installation and Always Activate, and reboot. It's been a while, though, so maybe I'm wrong. EDIT: And once the driver is activated you've got to go to your sound settings and choose it as the MIDI out device.
Couldn't find the option. I get these under the Setting menu: Wingroove Setup High Priority Display TXT Repeat No Titlebar MIDI-Out
Click Wingroove setup. In there is an option that says "always activate" which you should click on. You might also have to open a program called "always activate" which should have a link in the start menu in order to get it working.
It's greyed out, and the program doesn't seem to be doing anything. I'll reboot my computer later and see if anything changed, though.
Or you can use TiMidity (and whatever it's Windows port is called) in conjunction with a buttload of Soundfont-combinations, works quite well for me on here, anyhow.
I am with Oerg and say that Yamaha S-YXG50 (or other stuff in the series) kicks assm but I still prefer what y Yamaha YMF718 sound card is doing, despite some flaws in it, its instruments and percussions are nicer to me.
I personally use FluidSynth along with the Fluid Soundfont and a MIDI loopback driver. If you want a quick and easy way to use FluidSynth, then install QSynth and LoopBe1. If you are using XP and below, you can set the MIDI device in the Sound Control Panel applet. In Vista and higher, you will need additional software to set the MIDI device. QSynth can let you load the soundfont from within the interface. The Yamaha XG MIDI device softsynth is for 32-bit Windows 2000 and XP only. To me, it doesn't beat using FluidSynth with a really good soundfont.