i just bought a 32" hdtv... ps2 and dreamcast look great 
only one bad thing...the light gun doesnt work... 
very sad coz house of the dead look great...
anyway to make it work
? or light gun are only for regular tv 
thanks
Depends, did you want to play these lightgun games in progressive mode? If not, then make sure your HDTV is not internally upscanning the signal, and make sure its not doing something funny like outputing 100hz refresh. If you can not turn off these options, then you are screwed, and must go the IR sensor route dabone linked to.
If you were wanting to play lightgun games in progressive mode, then you have a couple other options. If your HDTV supports VGA in, then Dreamcast+DC-VGA box will work like a charm (may need to adjust contrast/brightness to max). If you don't have VGA input, you could use a RGB->Component transcoder. Certain PS2 lightgun games will also recognize a progressive display, not sure if the games can actually output progressive video, but if you upscan the 480i component to 480P, it will work). I've been able to play Time Crisis II and Vampire Night at 640x480@60hz.