New PC has difficulty playing HD video files

[True Colors]

I have some high definition video files(bit rates around 12mbps to 16mbps). I used to play these on a dual core computer system and everything was just fine.

I recently purchased a new quad core computer system and it has difficulty playing these exact same video files. The new computer has some slight jitter with the new files.

Here are the system specs for both machines

OLD COMPUTER
dual core dell optiplex 760
windows 7 professional, 64 bit
8 gigs of DDR2 ram
very good video card by Nvidia(450, I think)

NEW COMPUTER
quad core i7 intel processor
windows 8 standard, 64 bit
12 gigs of DDR3 ram
Radeon 7770 HD video card

I have tried a few things already to correct this problem.

1 - When I first started using this new PC, the driver for the video card was from september 2012. I updated the driver to the april 2013 release from the manufacturer website. This did not fix the problem.

2 - I have tried putting the HD video files I am trying to play on various different hard drives. I have tried playing them on an internal drive and also a couple of different external drives. This did not fix the problem.

3 - I have tried a couple of different video players(MPCHC, VLC, etc.). This did not fix the problem.

I am having a couple of other problems with this new PC. But I would like to tackle this issue that I just described here first.

Any thoughts, ideas, suggestions?

Thanks!!

TC

[jagabo]

Try disabling or enabling DXVA (hardware decoding) in the players. You may have to exit and restart the players for change to take effect.

[Bjs]

Other problems could show light on the problem.

Make sure system is using the correct, up to date chipset driver package for the mainboard and not that supplied by the host operating system.

[budwzr]

That was a mistake to go for a non-Nvidia card.

[Gramps]

If you are using the OS image that came installed on the machine from the store, check for and remove any demo crap that they may have installed. A lot of people will install their favorite antivirus without removing the demo version of another antivirus that came with the PC. The real-time scanning of two pieces of software may conflict with each other, causing a hard drive access slowdown.