Windows Media Player 12 stuttering

[A Bad Day]

I've noticed that sometimes the HD videos downloaded from Youtube I play don't stutter at all, and other times they have severe stuttering (which usually occurs in the evening).

There were no other programs running other than background tasks, the CPU usage was low, but the hard drive usage was always close to max.

Laptop: Asus N61jq
CPU: i7 720qm (1.6 GHz, quad core)
GPU: Radeon HD 5730, CCC driver 12.11 beta
RAM: 8 GB
OS: Windows 7 SP1 64-bit Home Premium

EDIT: In order to stop the stuttering, I have to set the slider to a previous part of the video I've already seen and then repeat it until the video is over.

 

[Deleted member 904905]

Evening is when people start arriving home from work and jump on the net for the night. What you experienced is just normal network congestion.

 

[A Bad Day]

No, I already downloaded the videos beforehand. I'm confused of why they're stuttering when being read from the hard drive.

 

[A Bad Day]

This is how my 320 GB hard drive is partitioned:

The F: partition is where the videos are stored in. I've tried defragging it, but it always stays at 31% fragmentation.

 

[Deleted member 904905]

That's because you don't have enough free space to do a defrag. Defrag wants ~20% free space. This almost full drive could also be the source of your problem.