Video playback through Virtualbox guest SLOW

I have a Windows 7 guest running on my Windows 7 host and I'm trying to play video on the guest but it runs terribly slow. The guest has guest additions installed with the experimental 3d pack (can't remember specifically what it's called), both 2d and 3d acceleration is enabled, 256mb of video memory allocated, 4Gb ram allocated, and 4 "Processors" allocated at 100% execution cap. My host pc has 16Gb ram, an i7-4770k overclocked to 4.6GHz, and a pair of GTX650Ti Boosts in sli. Is there a setting I'm missing or is Virtualbox just unable to handle this?

 

What version of VirtualBox are you running? If 4.3.14, downgrade to 4.3.12. Try forcing virtualbox.exe to use Nvidia GPU.

 

I'm on 4.3.12 and I've added virtualbox.exe to my program settings in Nvidia control panel with all settings forced to minimum (maximum performance) and it didn't change anything.

 

Turns out it was just because I was using Windows Media Player. VLC runs just about perfectly except there is some occasional stuttering which is unfortunately not good enough for what I wanted to do. Oh well.