Laptop connects to TV, no sound. Any advice pls?

I have a relately advanced technical problem here. I am really hoping I am not the first one who has bumped into it. I'd really appreciate if someone can offer advice.

I have a Lenovo T400 laptop, used to connect it to my Sony Bravia TV, via VGA + miniplug. Both picture and sound are good.

Now trying to use docking station DVI port, DVI-> HDMI adapter, HDMI-HDMI cable connect to TV HDMI IN 1 port for video. And miniplug->red+white RCA cable to sound ports together with HDMI IN 1 port. Video is ok, but no sound.

I called Sony TV support. I was convinced this is not a TV issue. Since I plug in the HDMI cable, the video is ok on HDMI IN 1. And then I unplug HDMI cable, plug in the miniplug->RCA sound cable, audio is ok on HDMI in 1. It's just video and audio don't work together at the same time, which is not right.

Sony support engineer said that this could be because my T400 trying to output sound via DVI port, althought it can't. But since TV has HDMI connection, it detects digital sound signal, and then ignored the analog sound from RCA sound cable. So the solution should be disable the sound output to DVI port, only through the miniplug output. She doesn't know how, neither do I.

I consider myself sort of semi tech savvy. I explored many different configurations in my WinXP OS. But none fixed the problem. Is there a magic/hidden option to disable the digital sound output?

Thanks in advance.

Thanks for the replies guys.

This TV has model Sony Bravia KDL-46V5100

I've tried to assigned the HDMI1 port as label "PC", didn't make difference. But I see no where in the menu allows me to change audio source for a certain port?

The TV manual.
_http://www.docs.sony.com/release/V5100_referencebook.pdf

In the above manual PDF, it does have an option which is
"Alt. Audio/MTS
This Audio feature for current program lets you select an alternate audio (if it is
available)."
Alternate audio is disabled for analog signals and for digital signals that do not have
audio streams.
MTS is available only for analog programs.

Unfortunately, I am seeing this option is disabled on me.

Yeah, I can either get a receiver or video+audio->HDMI convertor as workaround, but I am really seeking a solution without extra investment

The HDMI IN 1 port on Sony TV is indeed designed to support taking audio seperate from HDMI video. I have another Sony W serial living room TV worked this way with a HTPC for years. So at this point I am pretty confident that if I can find a way to completely disable the sound output from the video card, which is Intel 4500MHD, I can get it resolved.