You need a buffer between you Video Card and the venue's TV:
http://store.grandtec.com/ultimateez.html
Just go from your Computer's second head vga to the Vga IN of the adapter.
Then, you have your choice as to how you want to feed the venue's TV:
VGA
S-video
RCA
Or, when in doubt, feed the RCA out, of the adpater, to the RCA IN of an RF modulator and then COAX OUT of the RF Mod to the COAX IN of the Venue's TV, which should be set to Channel 3 or 4, depending on what your RF Mod is set.
I have two Venues that "sparked." An RCA at one club and a COAX at another. None caused a problem with my Video Card as I was using the above adapter.