Most laptops have cheap video cards made by Intel and truly suck-the-big-one for HD.
Sometimes for just 100$ more you get one with a dedicated, separate, video card NOT made by Intel, with it's own memory (not shared with system RAM). That alone makes a big difference.
I've played HD 1080p video MKV files on single core computers ever since Bluray came out, on my big screen TV, no problems, thanks to an NVIDIA video card that cost me 150$ with onboard HDMI.
Only 1 cable between the computer & HDTV, HD video, windows desktop, and SOUND, one easy plug.
You have no idea how PEEVED I was when I could not connect the Macbook Pro directly to my Samsung TV for both Video and Sound.
Just video !!! WTF Apple? What a waste of a 50$ adapter.
My old DELL laptop that's a dual-core and dedicated Nvidia video card with 1G of RAM plays MKV / AVCHD / AVI in all resolutions with no problems, even when the 2+ Gigs files are on an USB external hard drive.
That's my new home theater setup to replace the previous <big box home-made computer>. However, no HDMI. So I plug SVGA + mini-plug stereo the the Computer IN jacks on the Samsung LCD 52".
When I put my Sony memory card into the laptop, and use VLC to play back the AVCHD's, they show up fine.
The editing is better on the Mac though, and by converting everything "personal" to HD MOV format, I can play them / stream them on my iPhone and iPad, at home over Wifi or using my WAN IP address, anywhere in the world to myself.
The expertise level required is still high, just slowly becoming mainstream, no thanks to Corporate Hollywood Mafia Hooligans.