If your PC has VGA out then you need to by VGA to HDMI converter.
If your pc has DVI out then you need to buy DVI to HDMI converter.
Same for your receiver (which I dough it)
And what is the use of connecting LCD TV via HDMI using PC or receiver you will not see any different if the original video is not HDMI for example there are very few TV channels which transmit HDMI signals. But might be useful while watching from CD/DVD using HDMI supported DVD player