I have attached a standard stereo auxiliary cable with red/white sockets from my HP Slimline PC to my Philips LCD TV whci I am using as a monitor, but there is still no sound coming from the TV (with the PC as a source)
Perhaps the RCA (phono) sockets on the PC are 'audio in', rather than 'audio out?'.
Try making a connection between the regular (3.5mm stereo jack) speaker output to the TV's phono sockets with a lead like this one: http://www.maplin.co.uk/module.aspx?ModuleNo=3 1700&doy=18m11
(NB: You can often find them far cheaper in 'discount stores' or 'pound shops').