RF Modulator issues

[Kitbasher]

Are any of you guys familiar with RF modulators?  I have a MAME / HTPC box that connects to my older tv with a RF modulator.  Yesterday I hooked the box up to a PC monitor so I could read everything while I installed updated Itouch software for my wireless Logitech mouse and keyboard.  When I hooked it back up to the TV initially everything looked fine.  The boot screen was displayed on the TV up until win XP actually started up.  Then the screen went black.  It did not seem to be doing anything, no drive access or anything, so I hit restart.  Started up the same and got to the same place.  I unhooked every cable and reconnected them and tried again.  Now the screen turns yellow as soon as the computer starts.  I was just thinking there was something wrong with the TV on the old TNT2 card in the box, but this morning I hooked up my Phillips DVD player to the RF modulator and the screen reacts, but there is no picture displayed. What it shows is while the DVD player is off I get a ghost image of channel 4, and when the DVD player is on, I get a colored static pattern without any ghost images or sound.
Does anyone have any ideas?  Did I toast my RF modulator?

Specks:
Radio Shack RF modulator with S-Video and composite
Duron 800
ECS motherboard with SIS chipset
256 MB pc 133
TNT2 32 MB with tv out
Win XP pro
Using S-video cable to connect to RF modulator

[StephenH]

Try connecting a monitor to the VGA port on your computer.  If the TV out goes blank, it is probably that TV Out is not enabled in windows and/or you may have too high a resolution.   I would lower the resolution to 640x480, or even lower at 60HZ (Interlaced).

If this does not help, I would try reinstalling your video card drivers.