my computer is 3 year old, and using 15' monitor, if i wnat to change to 22" , what parts do i need? please help! thanks !

I thought you can just get a new 22" monitor and plug it into your computer.  But it also depends on what type of input you want to use, you want to make sure your video card (or people call it graphic card) supports that.  The traditional screen uses VGA.  But if your new monitor is a HD monitor and you want to take advantage of that, then you will need to get a video card that supports HDMI.  And instead of connecting the monitor and computer using a VGA cable, you will need to buy a HDMI cable.

Hope that helps.

I believe VGA supports HD, VGA cable can be used to connect to HD monitor with no loss of quality.
If I didn't remember wrong, VGA is merely a compression of the signal and involves no conversion nor encoding

Ohhh!  Is that right?  Now when I think about it, I am wondering how they set up the media PC?  When I connect blu-ray player with TV, HDMI already contains video and audio.  So if a video card supports HDMI, the video card can't be transmitting audio signal too, does it?  So maybe people just hook up using VGA or S-Video, and then connect the audio separately from sound card to TV / receiver?

i am no expert in media, but i believe that's what they can do, connect with VGA for video and then connect audio separately with 3.5mm, this will still give HD with no quality loss
S-Video will lose quality though

When you buy 22" LCD now, most of the monitors should come with VGA and DVI connectors, some have only VGA(cheap one). some have VGA, DVI, and HDMI.  You have to check your video card output ports, it is support VGA and/or DVI, also make sure your video card  Maximum Resolution is equal or more than your LCD, otherwise you will get a very icon on screen. Each connectors is using different cable, you cannot use VGA cable for DVI or HDMI.  If you get a 22" wide screen, make sure your video card have a driver to support it, if not, you will waste the space on screen.