How do i connect acer 2420 to the tv,it dosen't have s video port?

You can connect your Laptop to a TV either using an RCA / s-video conversion cable (which connects to the VGA-out on the rear of your laptop)

Some TVs have a PC-in socket, which allows you to use a HD15 VGA cable to your TV instead IMHO this gives better video quality (depending on your TV).

To connect the audio you will need to convert the Headphone/Line out socket on your laptop to match your TVs inputs for the channel you are using (Usually this is RCA) so you will need a RCA/Phono audio cable (L+R) and an adapter to convert to 3.5mm stereo male. (ensure that your laptop volume is turned up to max, as you will use the TVs vol setting to change the volume once connected)

once you have all the cables connected up you switch your TV to the appropriate AV channel, and then switch to the external display on your laptop (using Fn+F5) remembering to set your screen resolution to suit your TV/external display

you can also use this to connect your laptop to a projector

There is an adapter that plugs into you VGA port, and turns it into s video and RCA outputs.

I found one online for less than $4. Here is the link:

http://cgi.ebay.com/VGA-to-TV-S-Video-RCA-AV-OUT-Converter-Adapter-Cable_W0QQitemZ360137975228QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item360137975228&_trksid=p3286.c0.m14&_trkparms=72%3A1234|66%3A2|65%3A12|39%3A1|240%3A1309|301%3A0|293%3A1|294%3A50

Hope this helps!