needed software to play HDTV and PDTV

i tried to play some tv episodes on quicktime...i was told i may need more software and sent to quicktime webpage. i just bought this macbook two weeks ago, what software do i need?

Abilty to playback TV episodes in QT Player is dependent on codecs used to encode these files. QT compatible files should play without problem. Third party propriatary fomats may require other (appropriate) QT components be installed or use of separate player capable of playing these unsupported formats.

" what software do i need?"
Lots. As much as your budget allows.
And many of these third party codecs will not yet be available for the new Intel Mac.
Many of the "off screen" recorders encode as MPEG-2 format to their internal HD's so you'll need lots of third party software (plus the Apple MPEG-2 Playback Component) to "convert" the files to QuickTime playback formats.
MPEG Streamclip (free) is a good start.
Use the "Movie Info" window of the QuickTime Player app to note what codecs are used. Download and install those appropriate for your OS.
If the file gives a (-2048) error it is probably in MPEG-2 format.

The Movie Info window shows a line named "Format:" (no quotes).
This is where you determine what codecs were used in the file creation and can help you on the download search for the proper versions for your machine.

Yep. Makes perfect sense to me.
Your new Intel Mac has some out of date (or missing) video and audio codecs that are not yet supported on the Intel Mac OS.
You need an XVID codec that runs on an Intel Mac. A Google search found:
http://www.mikecpeck.com/2006/04/play-xvid-movies-on-intel-mac.php
I don't trust beta software. Maybe you should just wait a while.