I can't speak for why the hotkey toggle doesn't work, but you should be able to switch to the S-Video port without problems (i.e. without the VGA port restriction you suggested). At the very least, the video card should have a tab for this (under Control Panel).
That being said, you'll probably be disappointed with the video quality, as S-Video only displays 480 lines of resolution. If "PC input" means the display has a 15-pin PC monitor port, use that - the resolution via this method is equivalent to HDMI/DVI/composite.
If it doesn't have this port, your best bet is probably an adaptor which converts PC monitor out to component. I believe ATI, among others, makes these.
I have a Dell Lattitude notebook, and the Phillips PF429630A Plasma. The TV has PC input as one of the features, and supports the following connection types:
My Dell Lattitude has VGA and S-Video out.
I thought it would be as simple as plugging the S-Video straight from the TV to the PC, and then using the Alt+F8 key to toggle the screen output... apparently this doesnt work.
My guess is the Alt+F8 function only works when I use the VGA connection, so if this is the case, how can I get the S-Video to appear on the TV -OR- is there a cable out there that can convert VGA to either HDMI, Composite, S-Video, or Component?